Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

¹²CO observations of the molecular cloud encompassing Sharpless 222 (LK Hα101) Christie, Richard Allan 1981

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1981_A6_7 C52.pdf [ 7.32MB ]
Metadata
JSON: 831-1.0085210.json
JSON-LD: 831-1.0085210-ld.json
RDF/XML (Pretty): 831-1.0085210-rdf.xml
RDF/JSON: 831-1.0085210-rdf.json
Turtle: 831-1.0085210-turtle.txt
N-Triples: 831-1.0085210-rdf-ntriples.txt
Original Record: 831-1.0085210-source.json
Full Text
831-1.0085210-fulltext.txt
Citation
831-1.0085210.ris

Full Text

1 2CO OBSERVATIONS OF THE MOLECULAR CLOUD ENCOMPASSING SHARPLESS 222 (LK HOflOl) by RICHARD ALLAN CHRISTIE .Sc., The U n i v e r s i t y of B r i t i s h Columbia, 197 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF PHYSICS We accept t h i s t h e s i s as comforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA August 1981 © R i c h a r d A l l a n C h r i s t i e , .1981 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of P H V S I C S The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 DE-6 (2/79) i i ABSTRACT The 4.57 meter m i l l i m e t r e wave t e l e s c o p e at the U n i v e r s i t y of B r i t i s h Columbia has been used to p a r t i a l l y map a region around Lk Hiy.101 one h a l f degree i n diameter c e n t e r e d on #(1950) = 04 H26 M34^0 ( r i g h t a s c e n s i o n ) , 6(1950) = 35°13'00" ( d e c l i n a t i o n ) i n the J=1—0 t r a n s i t i o n of 1 2 C 1 6 0 . Our 1 2CO r e s u l t s show a wide region of 1 2CO emission, but the exact boundaries are as yet undetermined. The n o r t h and west boundaries have been determined. We suspect the emission extends as f a r as a v i s u a l e x t i n c t i o n of 1 magnitude which covers a region almost one degree a c r o s s and s e v e r a l degrees long. The average r a d i a t i o n temperature, T* , i s 10 R. Within our survey f i e l d we found a l a r g e fragmented area with f i v e hot spots (20 K). Since 1 3CO o b s e r v a t i o n s were not made 1 3CO data was generated from the 1 2CO o b s e r v a t i o n s . Both the 1 2CO and 1 3CO temperature contours have f i v e hot spots w i t h i n a s i n g l e envelope of c o l d e r CO emission l o c a t e d southeast of Lk H«1 0 1 . Three CO c l o u d s (#1, #2, and #3) are r e s o l v e d at Lk HC<101 (7.2,-10.8), Lk HO(101 (0.0,-10.8), and LkHoqOl (7.2,-5.4). T h e i r masses were c a l c u l a t e d from the generated 1 3CO column d e n s i t i e s and are 49M 0, 41M©, and 25M @ r e s p e c t i v e l y . Two other c l o u d s (#4 and #5) on the l i m i t of r e s o l u t i o n are l o c a t e d at Lk H0<101 (3.6,-5.4) and Lk Hon01 (0.0,-1.8) and have masses of 11M 0 and 25M 0. Each of these fragments i s embedded i n the same 13 K 1 2CO contour centered on Lk HC*101 (3.6,-7.2). The mass i s c a l c u l a t e d from the f a b r i c a t e d 1 3CO data and should not be r e l i e d upon very s t r o n g l y . I t i s i n e r r o r by at most a f a c t o r of i i i two. Peak HI emission contours (Dewdney and Roger 1981) are a n t i c o r r e l a t e d to our peak CO co n t o u r s . The HI l i e s to the northwest. T h i s i n d i c a t e s that the peak CO and HI f e a t u r e s are l o c a t e d i n d i f f e r e n t r e g i o n s . The peak HI column d e n s i t i e s d e r i v e d from both the f a b r i c a t e d 1 3CO data and HI o b s e r v a t i o n s agree. They are ~1.3 x 1 0 2 1 atoms cm - 2. From s t a r counts we made of the region we see that the stronger CO emission c o r r e l a t e s with regions of stronger v i s u a l e x t i n c t i o n . The peak HI occurs where the e x t i n c t i o n i s low. The e x c i t i n g s t a r has presumably been able to d i s s o c i a t e H^ i n t o HI to the northwest where the v i s u a l e x t i n c t i o n i s lower. Dewdney and Roger (1981) have modelled t h i s asymmetry reasonably w e l l by assuming there i s a steep d i s c o n t i n u i t y of d e n s i t y near Lk HCV101 to the e a s t . The p o s i t i o n s of i n f r a r e d s t a r s from the Steward Observatory Near I n f r a r e d Photographic Sky Survey provide meager evidence f o r the ' B l i s t e r ' model ( I s r a e l 1977, Gilmore 1978) and suggest that s t a r formation was i n i t i a t e d on the edge of the c l o u d and proceeded inwards. Our CO hot spots c o u l d w e l l be the next g e n e r a t i o n of i n f r a r e d s t a r s . C o n f i r m a t i o n w i l l r e q u i r e a more complete map with b e t t e r r e s o l u t i o n of the region around Lk H0(101 (3.6,-7.2). i v TABLE OF CONTENTS Ab s t r a c t .n Table Of Contents i y L i s t Of F i g u r e s V L i s t Of Tables vi Acknowledgements V i i I. INTRODUCTION 1 I I . DATA ACQUISITION 6 I I . 1-Site 6 11.2- Equipment 7 11.3- Observing Sequence 10 11.4- On-Site Data Handling 19 I I I . DATA REDUCTION AND ANALYSIS 21 I I I . 1 - C a l i b r a t i o n 21 I I I . 2-Representation Of Lk HW01 Through G l o b a l P l o t s — 31 I I I . 3 - 1 2 C O R a d i a t i o n Temperatures 36 III . 4-Generating Model For 1 3CO 41 111.5- Generated 1 3CO Column D e n s i t i e s 48 111.6- Star Counting Theory, Data And R e s u l t s 55 IV. DISCUSSION OF RESULTS 71 IV.1.1-Previous O b s e r v a t i o n s : I n t r o d u c t i o n 71 IV.1.2-Previous O b s e r v a t i o n s : HI R e s u l t s 78 IV.1.3-Previous O b s e r v a t i o n s : CO R e s u l t s 83 IV.2-Our Observations 86 V. CONCLUSIONS 103 B i b l i o g r a p h y 105 Appendix: T* ( 1 2CO) Contours At Constant V e l o c i t y 108 V LIST OF FIGURES F i g u r e 1-The Receiver 9 F i g u r e 2-Reference P o s i t i o n Spectrum 18 F i g u r e 3-Lk HOC101 (5. 4 ,-3 . 6 ) - T i p p i n g Curve C a l i b r a t i o n — . 28 F i g u r e 4-Lk HCX101 (5.4,-3.6)-OMC1(Or ion A) C a l i b r a t i o n .... 30 F i g u r e 5-Global P l o t ( T i p p i n g Curve C a l i b r a t i o n ) 33 F i g u r e 6-Global P l o t (OMC1(Orion A) C a l i b r a t i o n ) 35 F i g u r e 7-Integrated 1 2CO Contours 40 F i g u r e 8-T* ( 1 3CO) Vs. T* ( 1 2CO)/T* ( 1 3CO) R a t i o s 4 5 F i g u r e 9-Generated T* ( 1 3CO) Contours 4 7 F i g u r e 10-Generated N C O L ( 1 3 C O ) Contours 54 F i g u r e 11-A B E x t i n c t i o n Contours 63 F i g u r e 12-A H E x t i n c t i o n Contours 64 F i g u r e 13-Av E x t i n c t i o n Contours 65 F i g u r e 1 4 - I n f r a r e d Diagram 77 F i g u r e 15-HI Contour Map, F e l l i And Churchwell (1972) 80 F i g u r e 16-HI P r o f i l e , Dewdney And Roger (1981) 81 F i g u r e 17-3-D D i s p l a y Of HI R e s u l t s 82 F i g u r e 1 8 - 1 2 C 0 P r o f i l e Dip 85 F i g u r e 1 9-Comparison Of 1 2CO, HI, A v Etc 1 0 2 NOTE: SIX OVERLAYS OF THE RESULTS FOR FIGURE 19 . . . . i n pocket v i LIST OF TABLES Table I-Observation D e t a i l s 14 Table I I - T * ( 1 3CO) Generating Model 44 Table I l l - P r o f i l e Half Width R a t i o s 51 Table I V - V e l o c i t y C a l c u l a t i o n s 52 Table V-Van R h i j n ' s Table For b = -9.0° 61 Table VI-Data Summary 67 Table V l l - I n f r a r e d Star P o s i t i o n s 75 Table VHI-Peak N C O L( 1 3CO) And R e l a t e d hv 98 Table I X - V i r i a l Cloud Masses 99 Table X-N f n L( 1 3CO) Cloud Masses 100 v i i ACKNOWLEDGEMENTS I wish to thank my t h e s i s s u p e r v i s o r , Dr. W.H. McCutcheon, fo r h i s continued encouragement and suggestions d u r i n g the course of t h i s p r o j e c t . I thank the other members of our group, Dr. W.L.H. Shuter and Mr. C P . Chan f o r t h e i r v alued c o n t r i b u t i o n s . F i n a l l y , I would l i k e to thank three groups f o r t h e i r generous c o n t r i b u t i o n of unpublished data on Sharpless r e g i o n s : Drs. P. Dewdney and R. Roger at the Dominion Radio A s t r o p h y s i c a l Observatory (D.R.A.O.), f o r t h e i r Sharpless 222 HI r e s u l t s , Dr. E. Cra i n e of the Steward Observatory, f o r sending a p r i n t of Sha r p l e s s 222 from t h e i r i n f r a r e d sky survey and Dr. P. Jackson of the U n i v e r s i t y of Maryland f o r sending a" copy of J . Sewall's second year p r o j e c t c o v e r i n g 1 2C0 and 1 3 C 0 o b s e r v a t i o n s f o r three S h a r p l e s s r e g i o n s . 1 I. INTRODUCTION The J=1—*0 t r a n s i t i o n of i n t e r s t e l l a r 1 2 C 1 6 0 was f i r s t d e t e c t e d by Wilson et a l . (1970). Penzias et a l . (1971) found that CO column d e s i t i e s are s y s t e m a t i c a l l y higher near HII r e g i o n s . I t i s now accepted that CO emission, along with emission from other molecules and maser l i n e emission, are of t e n i n d i c a t o r s of recent s t a r formation. The use of CO emission as a probe of i n t e r s t e l l a r molecular clouds was recognized at once. CO i s the most abundant i n t e r s t e l l a r r a d i o molecule, and i t s r e l a t i v e l y long l i f e t i m e means that the J=1 l e v e l can be populated even i n re g i o n s with small e x c i t a t i o n r a t e s . Penzias et a l . (1972) showed that t h i s l e v e l c o u l d be we l l populated i n t y p i c a l molecular clouds through c o l l i s i o n s between CO and n e u t r a l hydrogen molecules. They a l s o found that i f the J=1—>0 t r a n s i t i o n was o p t i c a l l y t h i c k i n a unif o r m l y dense c l o u d , t h e r m a l i z a t i o n of the t r a n s i t i o n would be assured by the r a d i a t i v e t r a p p i n g of the J=1—>-0 photons. Wherever the J=1—*0 t r a n s i t i o n f o r 1 2CO has been detected i t has been found to be o p t i c a l l y t h i c k and hence i t can be used to determine the k i n e t i c temperature. 1 3CO i s not u s u a l l y s a t u r a t e d s i n c e i t i s f a r l e s s abundant than 1 2CO. As a r e s u l t , 1 3CO i s g e n e r a l l y used as a d e n s i t y probe. In some cases even 1 3CO has a high o p t i c a l depth (Sewall 1980). For t h i s reason i t would be b e t t e r to use the even l e s s abundant 1 2 C 1 8 0 is o t o p e f o r probing dense c l o u d c e n t r e s . The cause of the observed CO l i n e widths has sparked c o n s i d e r a b l e c o n t r o v e r s y . The thermal l i n e width, assuming 2 t y p i c a l parameters f o r a molecular c l o u d , i s about 0.1 km s ~ 1 . Observations i n d i c a t e l i n e widths many times l a r g e r . G e n e r a l l y , these l i n e widths would correspond to supersonic d i s p e r s i o n v e l o c i t i e s . I f the l i n e widths are caused by t u r b u l e n t motions, tremendous sources of energy are r e q u i r e d to prevent r a p i d damping. G o l d r e i c h and Kwan (1974) proposed that the l i n e widths are due to sys t e m a t i c , r a t h e r than t u r b u l e n t , motions. Since the l i n e p r o f i l e s of d i f f e r e n t i s o t o p i c s p e c i e s g e n e r a l l y have s i m i l a r appearances and show analogous v a r i a t i o n s throughout the cl o u d , they argued that the cloud s are undergoing some systematic motion such as g r a v i t a t i o n a l c o l l a p s e . G o l d r e i c h and Kwan (1974) found that the clouds c o o l e d f a s t e r by CO emission than they c o u l d be heated by a d i a b a t i c compression and the r e l e a s e of g r a v i t a t i o n a l energy. For very warm clouds (TK£- 25 K) the temperatures i m p l i e d by the CO l i n e i n t e n s i t i e s c o u l d be maintained by c o l l i s i o n s between the gas molecules and the dust g r a i n s heated by b u r i e d p r o t o s t a r s . The frequent a s s o c i a t i o n of CO emission with s t r o n g i n f r a r e d p o i n t sources i s evidence i n favor of t h i s model. The l a r g e v e l o c i t y g r a d i e n t model accounts f o r most CO l i n e shapes, but there are some strong opposing arguments. These are summarized by Zuckerman and Palmer (1974). We w i l l d i s c u s s one of these arguments more f u l l y i n s e c t i o n IV.3. To o b t a i n a more d e t a i l e d d e s c r i p t i o n of s t a r formation one needs to i n c o r p o r a t e complicated hydrodynamic processes such as t u r b u l e n c e , clumping, and eddies i n c l o u d models. When CO and Hoc v e l o c i t i e s near an HII region are a v a i l a b l e one g e n e r a l l y f i n d s the Hex v e l o c i t y to be more negative than the CO v e l o c i t y . T h i s suggests that i o n i z e d m a t e r i a l i s streaming 3 away from the n e u t r a l m a t e r i a l which g i v e s r i s e to the CO e m i s s i o n . Such o b s e r v a t i o n s have l e d to the ' B l i s t e r ' model ( I s r a e l 1977, Gilmore 1978). In t h i s model OB a s s o c i a t i o n s form j u s t i n s i d e the s u r f a c e s of huge elongated molecular clouds where they give r i s e to ultracompact HII r e g i o n s . The s t a r formation process i s i n i t i a t e d on one s i d e of the c l o u d complex and a u t o c a t a l y t i c a l l y proceeds i n t o the c l o u d . Compact HII regions are g e n e r a l l y found near the edge of c l o u d s . The t r i g g e r i n g mechanism for s t a r formation i s b e l i e v e d to be the passage of shocks i n t o the n e u t r a l c l o u d s . Star formation i s perhaps i n i t i a t e d by supernovae and/or s p i r a l d e n s i t y waves. Subsequent generations are formed by the shock waves from the r e c e n t l y generated s t a r s (Elmegreen and Lada 1977). The Champagne model (Tenorio-Tagle 1979) g i v e s s i m i l a r r e s u l t s using numerical modeling. Habing and I s r a e l (1979) give the f o l l o w i n g e v o l u t i o n a r y sequence f o r compact HII r e g i o n s . "1. The youngest o b j e c t s are i n f r a r e d sources without any HII r e g i o n s , a s s o c i a t e d , i f at a l l , only with HgO masers having simple l i n e p r o f i l e s . These o b j e c t s may be i d e n t i f i e d with a c c r e t i n g s t a r s . ... 2. S l i g h t l y o l d e r are those o b j e c t s which are s i m i l a r , but which i n a d d i t i o n show high v e l o c i t y peaks in the H a0 maser l i n e p r o f i l e s ; these peaks i n d i c a t e the e x i s t e n c e of a s i g n i f i c a n t s t e l l a r wind, implying the end of the a c c r e t i o n phase. ... 3. Next are the i n f r a r e d sources a s s o c i a t e d with the s m a l l e s t HII regions ( 3 X 1 0 1 6 cm diameter). ... Apparently the HII region has grown s u f f i c i e n t l y i n s i z e to become v i s i b l e . Surrounding the HII region i s a dense s h e l l that sometimes houses an OH maser source. 4. When the HII region has expanded beyond a diameter of 3 X 1 0 1 7 cm, the OH maser disap p e a r s and a b l i s t e r - t y p e HII region w i l l soon appear." 4 Why map 1 2 C 0 emission i n Sh a r p l e s s 222? The r e s u l t s of prev i o u s work, summarized i n s e c t i o n IV.1, show Sharpless 222 to be a young, compact HII region with a very strong p o s s i b i l i t y of ongoing s t a r formation. Recently Dewdney and Roger (1981) have mapped t h i s r e g i o n i n the HI l i n e emission with an angular r e s o l u t i o n of 2 arcminutes. In c o n j u n c t i o n with t h e i r work we decided to map the molecular c l o u d encompassing Sharpless 222. G e n e r a l l y HI and CO sample d i f f e r e n t c o n s t i t u e n t s of a region and t h i s would provide a d d i t i o n a l p o s s i b i l i t i e s f o r i n t e r p r e t a t i o n . The HI and CO o b s e r v a t i o n s a l s o have approximately the same s p a t i a l and v e l o c i t y r e s o l u t i o n . T h i s would make any comparison between the HI and CO o b s e r v a t i o n s more meaningful. As w e l l , the approximate s i z e i n d i c a t e d by the outermost HI contour c o u l d be mapped with a beam width of s e v e r a l arcminutes in a reasonable time. In r e t r o s p e c t , the l a t t e r was a c t u a l l y a poor assumption. Our o b s e r v a t i o n s have shown the extent of the c l o u d i s f a r grea t e r than we had a n t i c i p a t e d . As a r e s u l t of t h i s and time consuming t e c h n i c a l d i f f i c u l t i e s with the t e l e s c o p e , we had to make a few compromises. F i r s t , we had to l i m i t the extent of our o b s e r v a t i o n s , so that we have determined only 60 per cent of the cloud's edge. Secondly, we c o u l d only p a r t i a l l y sample much of the o b s e r v a t i o n f i e l d . N e v e r t h e l e s s , S h a r p l e s s 222 has been a p a r t i c u l a r l y p r o f i t a b l e source to examine. I t has y i e l d e d many i n t e r e s t i n g phenomena and appears to be p r o t o t y p i c of molecular clouds engaged i n s t a r formation. For the purpose of t h i s p r o j e c t the name Sharpless 222 i s used to d e s c r i b e the molecular c l o u d encompassing the HII 5 region, NGC 1579, while Lk HC<101 denotes the associated source of the illumination. The one exception i s the use of LH101 to label plots and tables. 6 I I . DATA ACQUISITION I I . 1 - S i t e O bservations of the Sh a r p l e s s 222 region were c a r r i e d out using the 4.57 meter m i l l i m e t r e wave te l e s c o p e l o c a t e d on the U n i v e r s i t y of B r i t i s h Columbia campus i n Vancouver (Shuter and McCutcheon 1974, Mahoney 1976). The t e l e s c o p e i s s i t u a t e d at 123°13'56" West l o n g i t u d e , 49°15'11" North l a t i t u d e . The e l e v a t i o n i s about 50 meters above sea l e v e l . Operating at the 1 2CO frequency of 115.271 GHz, the te l e s c o p e has an e f f e c t i v e beam width of 0.044 degrees. The p o i n t i n g r e p e a t a b i l i t y of the t e l e s c o p e i s ±0.015 degrees. Source t r a c k i n g i s at worst ±0.03 degrees which amounts to the h a l f power beam spacing used as our map sp a c i n g . The beam e f f i c i e n c y i s about 37 per cent. 7 II.2-Equipment The r e c e i v e r uses a s i n g l e ended mixer with a g a l l i u m a r s e n i d e Schottky b a r r i e r diode. Both the s i g n a l mixer and the two stage parametric a m p l i f i e r are kept c o o l e d to 20 K i n a r e f r i g e r a t e d dewar at the focus of the t e l e s c o p e . At 115.271 GHz the system noise temperature f o r these o b s e r v a t i o n s averaged 1200 K (SSB). A schematic of the r e c e i v e r used i s given i n F i g u r e 1. Spectra were obtained using a 64 channel f i l t e r spectrometer. Each channel i s 250 KHz wide. The channel f r e q u e n c i e s range from 299.500 MHz to 315.250 MHz. Spectra were accumulated i n a Fabri-Tek s i g n a l averager and v a r i o u s forms of r e d u c t i o n c o u l d be c a r r i e d out by a NOVA 1200 minicomputer. The o n - s i t e programs were developed by Mahoney (1976). F u l l d e t a i l s of the o n - s i t e data h a n d l i n g are given i n s e c t i o n I I . 4 . 8 F i g u r e 1 -The Receiver F i g u r e 1 i s a schematic diagram of the 80 to 120 GHz c o o l e d r e c e i v e r a t the U n i v e r s i t y of B r i t i s h Columbia. The average system temperature, T $ Y S , i s about 900 K ( s i n g l e sideband) under normal o p e r a t i n g c o n d i t i o n s . ANTENNA | HUT I IF. MF, PIS SYNCHRONIZER P.5. REF. IF. 5*SE CMARr RicOHSER C80025 80-120 GHZ. RAPK3 ASmtWOMY IO/4/T9 C O O L E D R E C E I V E R 10 II.3-Qbservinq Sequence E i g h t y - n i n e p o s i t i o n s were observed i n the S h a r p l e s s 222 r e g i o n , at spacings of 0.03 degrees. The region observed would f i l l a c i r c l e one-half degree in diameter. Often a s p e c i f i c s p e c t r a l p o s i t i o n w i l l be w r i t t e n as Lk HCX101 (x.x,y.y) where the numbers f o l l o w i n g Lk HO(101 represent the o f f s e t s in r i g h t a s c e n s i o n and d e c l i n a t i o n i n arcminutes with respect to our nominal c e n t r e p o s i t i o n ; (X{ 1 950)=04 H26 M34to (Right Ascension) 6 ( 1950)=35°13'00':0 ( D e c l i n a t i o n ) T h i s c e n t r e p o s i t i o n was chosen as the approximate c e n t r e of the Dewdney and Roger (1981) HI map. As a r e s u l t , the i l l u m i n a t i n g s t a r Lk HCX101 i s l o c a t e d at Lk H0OO1 (5.4,-3.6). The s p e c t r a were obtained by a l t e r n a t i n g between ON source, S, scans and OFF source, R, or r e f e r e n c e scans in a load switched r e c e i v e r mode. The term scan r e f e r s to the process of o b t a i n i n g a spectrum by i n t e g r a t i n g on a s i n g l e f i x e d beam p o s i t i o n f o r 320 seconds. The purpose of o b t a i n i n g r e f e r e n c e scans i s to improve b a s e l i n e s t a b i l i t y and to s u b t r a c t r e c e i v e r n o i s e and sky c o n t r i b u t i o n s . C a r e f u l s e l e c t i o n of the r e f e r e n c e r e g i o n i s r e q u i r e d to o b t a i n a region f r e e of CO emission. A f t e r meticulous v i s u a l i n s p e c t i o n of the Palomar photographic p r i n t s we s e l e c t e d «(1 950) =04 H 26*51&. 7 , 6 ( 1 950) =34 °1 0' 00 '.'0 as our r e f e r e n c e p o s i t i o n . In the course of t h i s p r o j e c t we have c o l l e c t e d almost t h i r t y scans of the r e f e r e n c e r e g i o n . Summation 11 of these scans i n d i c a t e s there i s n e g l i g i b l e 1 2 C 0 s i g n a l in the re f e r e n c e r e g i o n . G e n e r a l l y the 1 2 C 0 s i g n a l i n the ref e r e n c e spectrum i s added to each of the map p o s i t i o n s . T h i s was not done i n our case since the maximum T A ( 1 2C0) i n the re f e r e n c e was much l e s s than the root mean square (rms) noise of the average p r o f i l e and can be n e g l e c t e d . The averaged r e f e r e n c e spectrum i s given i n F i g u r e 2. In order to determine the t o t a l amount of i n t e g r a t i o n time necessary to gi v e a s u i t a b l e s i g n a l to noise r a t i o we used the f o l l o w i n g observing format. Each spectrum was the sum of four c o n s e c u t i v e ON source minus OFF source p a i r s . We w i l l represent t h i s as f o l l o w s /SR/SR/SR/SR/. We decided that each map p o s i t i o n would r e q u i r e four scans which t o t a l 21 M2 0 s of i n t e g r a t i o n time. One t h i r d of our observing time i s spent moving the te l e s c o p e from one p o s i t i o n to another. Of the remaining time, one h a l f i s spent on the re f e r e n c e p o s i t i o n . I t was then decided that a b e t t e r e f f i c i e n c y f o r mapping had to be found. Szabo (1980) c o n s i d e r e d t h i s problem i n h i s t h e s i s . We have f o l l o w e d h i s recommendations, using the obs e r v i n g sequence //S,R S a/S 3R S H//. Here S, , S a, S 3 , and S 4 a l l represent d i f f e r e n t map p o s i t i o n s . T h i s sequence was repeated four times duri n g the observing p e r i o d to give the t o t a l i n t e g r a t i o n time d e s i r e d . Beam p o s i t i o n s using the same re f e r e n c e were kept f a r apart to minimize the e f f e c t of any c o r r e l a t e d n o i s e . The one d i f f e r e n c e between our observing sequence and Szabo's. (1980) was that he observed s i x t e e n d i f f e r e n t p o s i t i o n s each night whereas we observed four d i f f e r e n t p o s i t i o n s each four times. Szabo's (1980) method i s t e c h n i c a l l y b e t t e r s i n c e he spreads the data 1 2 f o r these p o s i t i o n s over four n i g h t s and uses the averaged c a l i b r a t i o n of these same evenings. However, we found no n o t i c e a b l e improvement using h i s method, and t h e r e f o r e , we chose our sequence s i n c e i t allows d a i l y o n - s i t e averaging of the four s p e c t r a . Each day we mapped Lk HK101 (5.4,-3.6) and 0MC1(Orion A) as c a l i b r a t i o n sources to check the accuracy of our r e l a t i v e c a l i b r a t i o n . OMC1 was observed at the beginning and end of each observing s e s s i o n to check the c o n s i s t e n c y of the atmospheric a t t e n u a t i o n . The sky temperature was monitored to check f o r v a r i a t i o n s in o p a c i t y . Approximately every h a l f hour the spectrometer was c a l i b r a t e d using the known sky temperature. I t was o r i g i n a l l y intended to f u l l y map the region around Lk HCX101. As the p r o j e c t proceeded, 12C0 emission was found to be more widespread than we had a n t i c i p a t e d and i t was decided that we co u l d no longer f u l l y sample the e n t i r e f i e l d of the cl o u d . The r e s u l t i n g map i s given i n s e c t i o n III.2. A small region around Lk HCX101 i s f u l l y sampled as w e l l as a c r o s s and dia g o n a l s t r i p s over a wide extent of the c l o u d to determine where the 12C0 emission decreases. Table I summarizes the dates, p o s i t i o n s and observing sequences used to obt a i n the s p e c t r a . A l s o i n c l u d e d i s an i n d i c a t i o n of the atmospheric a t t e n u a t i o n determined from antenna t i p p i n g measurements and the r e c e i v e r system temperature. 1 3 Table I -Observation D e t a i l s Table I g i v e s a l i s t of the s p e c t r a l p o i n t s and the dates they were observed. A l s o given i s the average atmospheric o p a c i t y at the beginning and end of each observing s e s s i o n , ( f i n nepers) and the system temperature, T S Y S (SSB). The c e n t r e (0.0,0.0) p o s i t i o n i s , (X ( 1 950 ) = 04 H26 M34^0 (Right Ascension) 8(1950) = 35°13'00V0 ( D e c l i n a t i o n ) Table I -Observation D e t a i l s Date day/month P o i n t s t s t a r t - end (SSB) 29/4 (+5.4,-7.2) (+5.4,+3.6) (+5.4,-5.4) (+5.4,+7.2) 0.319- 0 .373 1358 30/4 (10.8,-3.6) (+3.6,-3.6) (-3.6,-3.6) (-9.0,-3.6) (+0.0,-3.6) 0.377- 0 .375 1222 1/5 (-9.0,+5.4) (-9.0,-1.8) 0.460- 0 .456 1134 1&2/5 (-9.0,10.8) (-9.0,-10.8) 2/5 (10.8.+0.0) (-1.8,+0.0) (+5.4,+0.0) (-9.0,+0.0) 0.327- 0 .311 1186 3/5 (0.0,-10.8) (+0.0,+0.0) (+0.0,+5.4) (0.0,+10.8) 0.351- 0 .273 1134 4/5 (-5.4,-10.8) (-5.4,+0.0) (-5.4,+5.4) (-5.4,10.8) 0.298- 0 .345 988 4&6/5 (+5.4,-1.8) (5.4,-10.8) 6/5 (1.8,-10.8) (+1.8,-1.8) (+1.8,+5.4) (+1.8,10.8) 0.370- 0 .330 1224 7/5 (-1.8,-10.8) (-1.8,-1.8) (-1.8,+5.4) (-1.8,10.8) 0.360- 0 .327 1274 7&10/5 (+3.6,-5.4) (+3.6,+0.0) Date day/month P o i n t s X s t a r t - e n d (SSB) 10/5 (9.0,-10.8) (+9.0,-1.8) (+9.0,+5.4) (9.0,+10.8) 0.460-0.426 1142 19/6 (7.2,-10.8) (+7.2,-5.4) (+7.2,+3.6) (7.2,+10.8) 0.483-0.391 1638 7/7 (+0.0,-9.0) (+0.0,+9.0) (-7.2,+0.0) (+7.2,+0.0) 0.532-0.404 1342 8/7 (+0.0,-7.2) (+0.0,-1.8) (-3.6,+0.0) (+9.0,+0.0) 0.562-0.482 1370 9/7 (+0.0,-5.4) (+0.0,+3.6) (-10.8,0.0) (+1.8,+0.0) (+0.0,-1.8) 0.525-0.482 1524 18/7 (+0.0,+7.2) (0.0,-12.6) 0.684-0.491 1548 19/7 (+9.0,-7.2) (+3.6,-1.8) (+9.0,-5.4) (+3.6,+3.6) (+9.0,-3.6) (+3.6,-7.2) 0.700-0.530 1560 21/7 (0.0,-14.4) (0.0,+12.6) (-12.6,0.0) (12.6,+0.0) 0.682-0.505 1434 12/11 (+7.2,-7.2) (-3.6,+3.6) (+9.0,-9.0) (-1.8,+1.8) (+7.2,-3.6) (-5.4,-5.4) 0.503-0.425 1574 Date day/month P o i n t s r s t a r t -end (SSB) 15/11 (10.8,-10.8) (-9.0,+9.0) (+7.2,-1.8) (-7.2,-7.2) (+1.8,+1.8) (-9.0,-9.0) 0.505-0.485 1720 21/11 (-10.8,-10.8) (+5.4,+5.4) (-7.2,+7.2) (+7.2,+7.2) (-10.8,10.8) (+9.0,+9.0) 0.500-0.425 1870 Note (5.4,-3.6) corresponds to Lk HOO01 and was used as a c a l i b r a t i o n source. Consequently, i t was observed each of these days and s e v e r a l days before the o b s e r v a t i o n program began. A t o t a l of n i n e t y - f i v e scans were c o l l e c t e d g i v i n g a t o t a l i n t e g r a t i o n time of 8.44 hours. 17 F i g u r e 2 -Reference P o s i t i o n Spectrum The f i g u r e shown i s the average of twenty-eight 320 second scans f o r a t o t a l i n t e g r a t i o n time of 2.5 hours. The peak d e v i a t i o n from zero s i g n a l i s -1.72 k e l v i n . The rms noise of the spectrum i s 0.75 k e l v i n . A l s o i n d i c a t e d i s the average s p e c t r a l n o i s e f o r map p o s i t i o n s (dashed l i n e at 2.35 k e l v i n ) . The 1 2CO s i g n a l i n the r e f e r e n c e spectrum i s small even when compared with the average s p e c t r a l n o i s e . The r e f e r e n c e p o s i t i o n i s , 0^(1950) = 04 H26 M51^7 (Right Ascension) 6(1950) = 34°10 ,001 ,0 ( D e c l i n a t i o n ) 19 11.4-On-Site Data Handling A Fabri-Tek s i g n a l averager c o n t r o l l e d by a NOVA 1200 minicomputer was used f o r o n - s i t e data h a n d l i n g . Complete d e t a i l s of the programs and hardware are given by Mahoney (1976). Each ON source and OFF source p a i r was s t o r e d on papertape. A f t e r each day of o b s e r v a t i o n the four ON-OFF p a i r s f o r each map p o s i t i o n were averaged. No weighting a c c o r d i n g to the c a l i b r a t i o n was necessary s i n c e a l l the o b s e r v a t i o n s f o r a s i n g l e p o i n t were made on the same day using the same sky c a l i b r a t i o n . The averaged s p e c t r a were converted to an antenna temperature, T A , using the c a l i b r a t i o n tape f o r that day. Previous o b s e r v a t i o n s (Knapp et a l . 1976, Wilson et a l . 1973) had i n d i c a t e d the p o s s i b i l i t y of v e l o c i t y s t r u c t u r e i n the f a r wings of the s p e c t r a l l i n e . Although t h i s s t r u c t u r e would have appeared at the very edge of our b a s e l i n e s , we found no evidence of i t i n our data and consequently proceeded with the a n a l y s i s . The l a s t step of the p r e l i m i n a r y p r o c e s s i n g was to c o r r e c t the spectrum b a s e l i n e s by removing a second order polynomial f i t to those p o i n t s of the spectrum thought to have no s i g n a l ( u s u a l l y the f i r s t 25 and l a s t 22 channels of the 64 channel spectrometer). T h i s allowed us to c a l c u l a t e , 20 where c i s the channel number and S c i s the s i g n a l i n channel c. We adopted cr as the root mean square (rms) d e v i a t i o n f o r the spectrum. T h i s r e q u i r e s the mean to be zero. F i n a l l y , the data were not smoothed. Knapp et a l . (1976) noted a s e l f - a b s o r p t i o n l i k e f e a t u r e i n the middle of the 1 2CO s p e c t r a l l i n e . Our r e s u l t s c o n f i r m that there i s a prominent d i p in many of the s p e c t r a , which would be l o s t i f the data were smoothed (Figure 18). 21 I I I . DATA REDUCTION AND ANALYSIS  I I I . 1 - C a l i b r a t i o n T h i s s e c t i o n d i s c u s s e s the problems encountered i n f i n d i n g a r e l i a b l e c a l i b r a t i o n procedure f o r our temperature s c a l e . Absolute c a l i b r a t i o n f o r m i l l i m e t r e wave o b s e r v a t i o n s i s more of an a r t than a s c i e n c e . The r e l a t i v e temperature s c a l e i s f a i r l y easy to determine but an a b s o l u t e s c a l e i s f a r more e l u s i v e . We b e l i e v e our c a l i b r a t i o n method has given an a b s o l u t e s c a l e with a maximum e r r o r of 20 per cent. S p e c t r a l l i n e o b s e r v a t i o n s at r a d i o wavelengths are g e n e r a l l y c a l i b r a t e d i n a two step process. F i r s t , an observed s i g n a l i n t e n s i t y i s converted to an antenna temperature, T A . T h i s process assumes the Rayleigh-Jeans approximation. The observed s i g n a l i s compared to a c a l i b r a t i o n source with a known abs o l u t e temperature. A c a l i b r a t i o n spectrum from the synchronously d e t e c t e d d i f f e r e n c e output between the chopper wheel absorber at ambient temperature, T f l M B , and the sky was ob t a i n e d . The sky temperature, T 5 K r , was c a l c u l a t e d by measuring the d e f l e c t i o n s from an absorber at an e f f e c t i v e l i q u i d n i t r o g e n temperature of 85 K and an absorber at the ambient temperature p l a c e d i n f r o n t of the feed horn. T h i s was done at the beginning of each observing s e s s i o n . The end p o i n t s d e f i n e d by the two temperatures were checked at the end of each s e s s i o n . To ensure c o r r e c t d e t e r m i n a t i o n of the sky temperature we i n t e r p o l a t e d the r e s u l t s a c c o r d i n g to the change in the r e f e r e n c e end p o i n t s . G e n e r a l l y t h i s had an i n s i g n i f i c a n t e f f e c t on T S K y . On n i g h t s where the atmospheric o p a c i t y changed d r a m a t i c a l l y the sky 22 temperature c o r r e c t i o n helped e l i m i n a t e a p o t e n t i a l e r r o r . T S Ky was monitored approximately every h a l f hour and a f u l l t i p p i n g curve measurement was c a r r i e d out at the s t a r t and f i n i s h of each observing s e s s i o n . The second step i n the c a l b r a t i o n process i s to c o r r e c t the antenna temperature f o r atmospheric and antenna l o s s e s to determine the true b r i g h t n e s s temperature. The beam e f f i c i e n c y , ^ , was c a l c u l a t e d by comparing our measured T A at v a r i o u s secant z's (z i s the z e n i t h angle) to the standard values of T A f o r 0MC1(Orion A) and s e v e r a l other sources ( U l i c h and Haas 1976). We determined to be about 37 per c ent. At m i l l i m e t r e wavelengths there are a number of d i f f i c u l t i e s i n determining the atmospheric l o s s e s . T h i s i s p a r t i c u l a r l y true f o r J=1—>0 1 2 C 0 o b s e r v a t i o n s . One r e q u i r e s a knowledge of the r e l a t i v e sideband gains and how the a t t e n u a t i o n in the s i g n a l sideband can be r e l a t e d to the average a t t e n u a t i o n as a f u n c t i o n of z e n i t h angle, z, and sky temperature. There i s no convenient method to determine the s i g n a l and image gains s e p a r a t e l y . The 115.271 GHz 1 2 C 0 J=1—'0 s p e c t r a l l i n e frequency i s s i t u a t e d on the t a i l of a very s t r o n g l y absorbing oxygen l i n e and t h i s causes the two bands to have s i g n i f i c a n t l y d i f f e r e n t z e n i t h a t t e n u a t i o n s . The problem i s to determine the s i g n a l z e n i t h a t t e n u a t i o n , f s , and the image a t t e n u a t i o n , X{ . Our t i p p i n g curves are used to measure the average a t t e n u a t i o n , X • If a r e l a t i o n s h i p between Xs and t ; i s known, the s i g n a l a t t e n u a t i o n can be found. Two summer students at U.B.C. have worked on t h i s problem 23 f o r our t e l e s c o p e . From an i n t e r n a l r e port by Robert Braun (1980) on c a l i b r a t i o n procedures, we have an e m p i r i c a l r e l a t i o n f o r the average a t t e n u a t i o n X . r =. — ! — in L Sec 2 \(\+0.0\3L7 Sedll)flbg.<]*38. <\\'\*(T t^r^S)(\~ Sec where c _ j I J E C £ ' C O 5 E c o s (DEC) COS (HA) COS ( L ) + S\n (DEC) S I H ( L ) Here DEC i s the d e c l i n a t i o n of the source, HA i s the hour angle and L i s the l a t i t u d e of the t e l e s c o p e (49°25 N o r t h ) . By making p l o t s of T A m versus 7 f o r v a r y i n g T A„ 6(270,280,290,300) and secant z (1.0,1.1,1.3,1.6,1.8,2.2) we solve for r g r a p h i c a l l y . The r e l a t i o n i s weakly dependent on T A M 6 and s t r o n g l y dependent on secant z. From our t i p p i n g curves we obtained v a l u e s f o r T A r l 6 at s i x valu e s of secant z's and then used the graphs to f i n d X . Knowing T , we obtained % from a program developed by John de Bruyn (1979). De Bruyn's program 'Atmosphere' r e l a t e s and T-L from t h e o r e t i c a l c o n s i d e r a t i o n s . — 8 \ r = ( L O « I - o.ooa) T + ( o . i a 3 ± ^ x > o ) 24 and r . = ( o . i o q ± o.oox)r - ( 0 . 1 1 3 ± a * i c f 8 ) As we can see from these equations we have a l i n e a r r e l a t i o n between ts and "~t. U n f o r t u n a t e l y , t h i s r e l a t i o n s h i p d i d not always give good r e s u l t s . T A ( 1 2C0) f o r 0MC1 v a r i e d s i g n i f i c a n t l y from the accepted value of 60 K. The m a j o r i t y of our c a l i b r a t i o n e r r o r s l i k e l y a r i s e from some of the s i m p l i f y i n g assumptions r e q u i r e d by t h i s program (eg. a p a r a l l e l plane atmosphere). Once was determined we c o u l d c o r r e c t T A f o r both S e c Z atmospheric l o s s e s (£ ) and the beam l o s s e s (^ ) • The antenna temperature, T A , and the true source b r i g h t n e s s temperature, T A , f o r a p a r a l l e l plane atmosphere are r e l a t e d by, TA = T: % e x ? ( - ? s sec z ) Our data f o r Sharpless 222 were c a l i b r a t e d using two d i f f e r e n t methods. F i r s t , we c a l i b r a t e d a l l the data using the atmospheric a t t e n u a t i o n , X , from - our t i p p i n g curve measurements. The average temperature, TA ( 1 2CO), f o r OMC1(Orion A) was 55 ± 9 K where the 9 r e f e r s to the standard 25 d e v i a t i o n of any one measurement. The average temperature, T * ( 1 2 C 0 ) , f o r our second c a l i b r a t i o n source, ft Lk HOI101 (5.4,-3.6), was then found to be 12.8 K with an rms e r r o r of the mean of 0.5 K. Second, we c a l i b r a t e d the same raw data t h i s time s e t t i n g T * ( 1 2CO) for OMC1(Orion A) to be 60 K. Th i s gave a new value of Xs to use to c a l i b r a t e the Sharpless 222 s p e c t r a . In t h i s case the average temperature f o r Lk H0(101 ( 5 . 4 , _ 3 . 6 ) was 13.5 K with an rms e r r o r of 0.5 K. The two averaged p l o t s of our Lk H « 1 0 1 ( 5 . 4 , - 3 . 6 ) c a l i b r a t i o n source are given i n F i g u r e s 3 and 4. Two map p o s i t i o n s had T A ( 1 2CO) that appeared to be c o n s i d e r a b l y lower than that of the surrounding s p e c t r a . These were Lk H«i 01 ( 0 . 0 , - 3 . 6 ) and Lk HCX101 ( 7 . 2 , - 3 . 6 ) . A f t e r examining the data on the two days that these were observed i t was found that the temperature of the c a l i b r a t i o n source Lk Hon 01 ( 5 . 4 , - 3 . 6 ) f o r Lk Hon 01 ( 0 . 0 , - 3 . 6 ) was i n f a c t much too low. To c o r r e c t t h i s anomaly we s c a l e d the T A ( 1 2CO) of Lk Hon 01 ( 5 . 4 , - 3 . 6 ) f o r t h i s day up to the average T* ( 1 2 C O ) , namely 13.5 K. The point Lk Hon 01 ( 0 . 0 , - 3 . 6 ) was c o r r e c t e d using the new ts from the s c a l e d c a l i b r a t i o n source. The spectrum at Lk HW101 ( 7 . 2 , - 3 . 6 ) appears to have a bad channel l o c a t e d i n the p r o f i l e . T h i s r e s u l t s from a random D.C. o f f s e t that p e r i o d i c a l l y appears i n one or two channels of the spectrometer. I t was decided that there was no evidence to a l t e r t h i s spectrum and that i t should have been repeated. U n f o r t u n a t e l y , the te l e s c o p e experienced t e c h n i c a l d i f f i c u l t i e s throughout the remainder of t h i s p r o j e c t that prevented any more s p e c t r a being taken. 26 During four s e s s i o n s our t i p p i n g curves i n d i c a t e d a two component atmosphere that was dependent on z e n i t h angle. Each component had a d i f f e r e n t atmospheric a t t e n u a t i o n , T , and as a r e s u l t the c a l i b r a t i o n e r r o r s f o r these days were hi g h e r . We estimate that the e r r o r does not exceed 20 per cent. In c o n c l u s i o n , we b e l i e v e the bulk of our data has a maximum c a l i b r a t i o n e r r o r of 20 per c e n t . R e p e a t a b i l i t y checks at s e v e r a l g r i d p o s i t i o n s confirmed t h i s estimate. C a l i b r a t i o n i s a very t r i c k y procedure that r e q u i r e s c o n s i s t e n t checks and p r e c a u t i o n s to maintain r e l i a b l e r e s u l t s . We f e e l that a l l the p r e c a u t i o n s helped s i m p l i f y and reduce our c a l i b r a t i o n e r r o r s . For m i l l i m e t r e wave r a d i o astronomy c a r e f u l c a l i b r a t i o n procedure i s e s s e n t i a l to good data. 27 F i g u r e 3 -Lk HCXIOl (5.4,-3.6)-Tipping Curve C a l i b r a t i o n T h i s spectrum i s the average of n i n e t y - f i v e 320 second scans. The t o t a l i n t e g r a t i o n time i s 8.44 hours. The l o c a t i o n c o i n c i d e s with the e x c i t i n g s t a r Lk H<X101, #(1950) = 04W 26 M51!7 (Right Ascension) S ( 1 950 ) = 3 5 ° 1 0 ' o o ! ' o ( D e c l i n a t i o n ) The temperature was c a l i b r a t e d using the d a i l y t i p p i n g curve measurements. The v e l o c i t y i s the average f o r a l l n i n e t y - f i v e scans (rms e r r o r of the mean i s 0.07 km s " 1 ) . 29 F i g u r e 4 -Lk H«101 (5.4,-3.6)-OMC1(Orion A) C a l i b r a t i o n T h i s spectrum i s the average of n i n e t y - f i v e 320 second scans. The t o t a l i n t e g r a t i o n time i s 8.44 hours. The l o c a t i o n c o i n c i d e s with the e x c i t i n g s t a r Lk HCX101, CXO 950) = 04 H26 f 15l 5.7 (Right Ascension) 6(1950) = 35°10'001'0 ( D e c l i n a t i o n ) The temperature was c a l i b r a t e d u sing OMC1(Orion A) as the c a l i b r a t i o n source. T* ( 1 2CO) f o r CMC1(Orion A) was taken to be 60 K. The v e l o c i t y i s the average f o r a l l n i n e t y - f i v e scans (rms e r r o r of the mean i s 0.07 km s _ 1 ) . LH101 ( 1 ECO 5. 40. -3.6D) PERK TEMP -VELO C I T Y -RMS N 0 I 5 E -13.5 -1 .25 0. 3B T - 1 9 - 1 3 - 7 19* 1 - 1 (KM/SEC) 1 1 1 7 LO O 31 I I I . 2 - R e p r e s e n t a t i o n Of Lk H o n 01 Through G l o b a l P l o t s We present Sharpless 222 r e s u l t s i n two d i f f e r e n t complementary formats. The f i r s t i s contour p l o t s of d e c l i n a t i o n (DEC) versus r i g h t ascension (RA) f o r a f i x e d l i n e v e l o c i t y . The second i s that of g l o b a l p l o t s as shown i n F i g u r e s 5 and 6. We d i d not use c o l o u r contours s i n c e the U.B.C. computing c e n t r e does not have a f u l l c o l o u r g r a p h i c s package. The ce n t r e does have c o l o u r i n t e n s i t y c o n t o u r s . Szabo (1980) found these were u n s u i t a b l e s i n c e the human eye can not d i s t i n g u i s h the i n t e n s i t i e s p r o p e r l y . G l o b a l p l o t s have the d i s t i n c t advantage of showing the e n t i r e region and general f e a t u r e s q u i t e w e l l ; however i t i s d i f f i c u l t to see how smal l e r f e a t u r e s at d i f f e r e n t p o s i t i o n s c o r r e l a t e . The contour p l o t s show the smaller f e a t u r e s and t h e i r c o r r e l a t i o n s with p o s i t i o n very w e l l . In t h i s way we gain maximum in f o r m a t i o n i n r e l a t i v e l y simple formats. F i g u r e 5 i s the g l o b a l p l o t of the s p e c t r a l p o s i t i o n s c a l i b r a t e d using the atmosphere transparency determined from the antenna t i p p i n g measurements. One c o r r e c t i o n , Lk H O U 0 1 (0.0,-3.6), i s based on the Lk H6X101 (5.4,-3.6) c a l i b r a t i o n source. F i g u r e 6 i s the g l o b a l p l o t of the s p e c t r a l p o s i t i o n s c a l i b r a t e d using OMC1(Orion A) as a c a l i b r a t i o n source. The same c o r r e c t i o n f o r p o s i t i o n (0 . 0,-3.6) has been made. The c a l i b r a t i o n s made using OMC1 as the c a l i b r a t i o n source were found to be s l i g h t l y b e t t e r than those from the t i p p i n g curves. For t h i s reason we decided to use t h i s data f o r the remaining a n a l y s i s . F u l l d e t a i l s are given i n chapter IV. 32 F i g u r e 5 - G l o b a l P l o t ( T i p p i n g Curve C a l i b r a t i o n ) A l l e i g h t y - n i n e s p e c t r a l p o s i t i o n s are i n d i c a t e d . The temperature s c a l e i s 95.00 K i n - 1 and the L.S.R. v e l o c i t y range i s -23 to 24 km s " 1 . There i s one c o r r e c t i o n based on the Lk H<X101 (5.4,-3.6) c a l i b r a t i o n source. T h i s i s p o s i t i o n Lk H0HO1 (0.0,-3.6). The remaining s p e c t r a l p o s i t i o n s were c a l i b r a t e d u s i n g the d a i l y t i p p i n g curve measurements. The c e n t r a l p o s i t i o n i s , (XO 950) = 04 H26 M34 s.O (Right Ascension) 5(1950) = 35°13'00i'0 ( D e c l i n a t i o n ) 33 L H 1 0 1 •Ax*: UUxJ UU Uw M M UJ UJ UJ UJ U* "T^TB n r - F " -ri r*B =rf~D i£r ^rr =£D ^tn SIGHT RSCEHSION IflRCNINSl 34-F i g u r e 6 - G l o b a l P l o t (0MC1(Orion A) C a l i b r a t i o n ) A l l e i g h t y - n i n e s p e c t r a l p o s i t i o n s are i n d i c a t e d . The temperature s c a l e i s 89.80 K in ~1 and the L.S.R. v e l o c i t y range i s -23 to 24 km s - 1 . There i s one c o r r e c t i o n based on the Lk H«101 (5.4,-3.6) c a l i b r a t i o n source. T h i s i s p o s i t i o n Lk HW101 (0.0,-3.6). The remaining s p e c t r a l p o s i t i o n s were c a l i b r a t e d using OMC1(Orion A) as the c a l i b r a t i o n source. T* ( 1 2CO) f o r OMC1 was taken to be 60 k e l v i n . The c e n t r a l p o s i t i o n i s , o(( 1950) = 04 H26 M34. S0 (Right Ascension) 8(1950) = 35°13'00"0 ( D e c l i n a t i o n ) * A v * WW ."t*A»* f»Av -»A*ft; LA* * A * : L A . -I±B nto r"D— — = 0 ^ r -RIGHT nscrasiw IRROIINS) * =+s ^ =An 36 I I I . 3 - 1 2 C O R a d i a t i o n Temperatures The v e l o c i t y r e s o l u t i o n a v a i l a b l e i s determined by the bandpass of the spectrometer. Our spectrometer has f i l t e r widths of 250 KHz which corresponds to a v e l o c i t y r e s o l u t i o n of 0.65 km s - 1 at the J=1—*0 t r a n s i t i o n of 1 2CO. The frequency counter used to check the c r y s t a l frequency i s a c c u r a t e only to about 125 KHz. The main reason f o r t h i s i s the d r i f t of the c r y s t a l frequency i t s e l f . To minimize t h i s problem the counter was c o n t i n u a l l y monitored such that the r e s u l t i n g e r r o r never exceeded 125 KHz. Another e r r o r that has subsequently been c o r r e c t e d l i e s i n our L o c a l Standard of Rest (L.S.R.) program. The v e l o c i t y r e s u l t i n g from the ear t h ' s motion i s s u b t r a c t e d from the observed v e l o c i t y i n f o r m a t i o n . Our program, d e s c r i b e d in Mahoney (1976), d i d not take p a r t i a l J u l i a n days i n t o account when c a l c u l a t i n g the L.S.R. Subsequent a n a l y s i s has shown that the maximum e r r o r i n c u r r e d i s l e s s than one h a l f a spectrometer channel. Summing over the p o s s i b l e sources of v e l o c i t y e r r o r s we see t h a t the t o t a l e r r o r i s at the l i m i t of our r e s o l u t i o n . T h i s i s 0.65 km s"'. In determining the c e n t r a l v e l o c i t y of the s p e c t r a l p r o f i l e f o r S h a rpless 222 we used two independent methods. The d i f f e r e n c e between the L.S.R. v e l o c i t i e s f o r Sh a r p l e s s 222 and OMC1(Orion A) at the beginning of our observing program was such that we c o u l d j u s t f i t both s p e c t r a i n t o the spectrometer bandpass using the same c r y s t a l frequency. T h i s was done by s w i t c h i n g between two l o c a l o s c i l l a t o r s spaced 8.0 MHz. a p a r t . Since we know the frequency d i f f e r e n c e between the two 37 o s c i l l a t o r s to a high degree of accuracy we c o u l d c a l c u l a t e the r e s u l t i n g S h arpless 222 p r o f i l e v e l o c i t y . We assumed a v e l o c i t y f o r the 1 2 C 0 p r o f i l e in 0MC1(Orion A) of 9.0 km s - 1 . T h i s gave a v e l o c i t y f o r Sharpless 222 of -1.25 km s _ 1 f o r the (5.4,-3.6) p o s i t i o n . The second method used a c r y s t a l frequency designed to pl a c e a l i n e having V L S R = 0 km s _ 1 i n t o channel 33. The c e n t r a l v e l o c i t y f o r Lk HcnOl (5.4,-3.6) was found to be -1.25 km s - 1 as be f o r e . The s p e c t r a l p r o f i l e f o r OMC1(Orion A) i s about 5 km s~ 1 wide. Adoption of a c e n t r a l v e l o c i t y of 9.0 km s~~1 on such a wide p r o f i l e would normally have a l a r g e e r r o r a s s o c i a t e d with the v e l o c i t y s i n c e the c e n t r e of a wide l i n e i s not as p r e c i s e l y d e f i n e d as that of a narrow l i n e . Since OMC1(Orion A) was used as the primary c a l i b r a t i o n source we have 36 p r o f i l e s that give an average c e n t r a l v e l o c i t y of 8.92 km s~ 1 with an rms e r r o r of 0.04 km s ~ 1 . The standard d e v i a t i o n f o r any one measurement was 0.25 km s - 1 . T h i s r e s u l t agrees very w e l l with the assumed value of 9.0 km s~ 1 . I t should a l s o be noted that two very d i f f e r e n t procedures gave the same c e n t r a l v e l o c i t y f o r Sharpless 222. We have a t o t a l of 95 scans f o r the c a l i b r a t i o n source Lk H0(101 (5.4,-3.6). The average v e l o c i t y determined from these scans i s -1.25 km s _ 1 with an rms e r r o r i n the mean of 0.07 km s ~ 1 . The standard d e v i a t i o n of any s i n g l e measurement i s 0.33 km s - 1 which i s l e s s by a f a c t o r of two than our v e l o c i t y r e s o l u t i o n . Knapp et a l . (1976) obtained a c e n t r a l p r o f i l e v e l o c i t y f o r Lk H0M01 (5.4,-3.6) of approximately -1 ± 1 km s " 1 . T h i s i s i n e x c e l l e n t agreement with our r e s u l t s . From both s e t s of data c a l i b r a t e d using the two methods we 38 obtained T A ( 1 2C0) contour maps f o r f i x e d L.S.R. v e l o c i t i e s . Comparison of these contours i n d i c a t e s that they are very n e a r l y i d e n t i c a l . F i g u r e 7 shows the T A ( 1 2C0) contour map i n t e g r a t e d over a l l L.S.R. v e l o c i t i e s . To check the. r e a l i t y of the contour f e a t u r e s we v a r i e d the f i x e d v e l o c i t y by small increments. We found the changes in the f e a t u r e s were n e g l i g i b l e , c e r t a i n l y f a r l e s s than our v e l o c i t y r e s o l u t i o n . The s p a t i a l r e s o l u t i o n of most of the f e a t u r e s on the T A ( 1 2 C 0 ) contours i s only m a r g i n a l . Unresolved f e a t u r e s c o u l d be caused by i n c o r r e c t c a l i b r a t i o n f o r one g r i d p o s i t i o n and consequently the r e a l i t y of these f e a t u r e s may be suspect. Due to t h i s f a c t , we cannot say very much about the s t r u c t u r e or s p a t i a l d e t a i l s of S h a r p l e s s 222. F u l l d e t a i l s of the s t r u c t u r e and s i z e of our c l o u d are given i n chapter f o u r . 39 F i g u r e 7 - I n t e g r a t e d 1 2 C 0 Contours The T^ ( , 2C0) i s i n t e g r a t e d over a l l v e l o c i t i e s to g i v e F i g u r e 7. The d e c l i n a t i o n (DEC) versus r i g h t a s c e n s i o n (RA) p l o t shows the f i v e h o t t e s t spots to be l o c a t e d at (7.2,-10.8), (0.0,-10.8), (7.2,-5.4), (3.6,-5.4), and (0.0,-1.8). The u n i t s for both a x i s are arcminutes. The c e n t r e (0.0,0.0) i s , 6VO950) = 0 4 H 2 6 M 3 4 ! o (Right Ascension) 5( 1950) = 35 °13 ' 00 ' . ' 0 ( D e c l i n a t i o n ) 4-0 RA. ARCMIN. °!2.0 9.333 6.667 4.0 1.333 -1.333 -4.0 -6.66-7 -9.333 -12=0 i i 1 I 1 • | 1 1 1 |-V •2.0 9.333 6.661 4.0 1.333 -3.333 -4.0 -6.66T -9.333 -32 0 Rfl. ARCMIN. 41 I I I . 4 - G e n e r a t i n q Model For 1 3 C 0 Although 1 3 C 0 ob s e r v a t i o n s were not made, approximate data can be generated. Two s i m p l i f y i n g assumptions have to be made. F i r s t , we need to know the r a t i o of the 1 2 C 0 to 1 3 C 0 emission temperatures. Secondly, we r e q u i r e the p r o f i l e h a l f widths f o r 1 3 C 0 . I t must be emphasized that these data are only a rough approximation and are not a good s u b s t i t u t e f o r r e a l o b s e r v a t i o n s . As a r e s u l t , the generated 1 3 C 0 data are used only to r e i n f o r c e the c o n c l u s i o n s apparent from the 1 2CO o b s e r v a t i o n s . In order to c a l c u l a t e the o p a c i t y of 1 3C0, T ( 1 3 C 0 ) , we r e q u i r e v a l u e s f o r the 1 3 C 0 r a d i a t i o n temperature, T A ( 1 3 C O ) , fo r each of the s p e c t r a l p o s i t i o n s . Recent data obtained by Sewall (1980) have been very b e n e f i c i a l i n t h i s regard. He found that the 1 3CO p r o f i l e s mimicked the 1 2CO p r o f i l e s i n shape and that the 1 3CO r a d i a t i o n temperatures were approximately f i v e times lower than those f o r the 1 2CO. F i g u r e 8 i s a p l o t of T A ( 1 3CO) versus the r a t i o of T A ( 1 2CO) to T A ( 1 3CO) f o r the three Sharpless regions s t u d i e d by Sewall (1980). The r e s u l t i s a power law r e l a t i o n that can be used to give an estimate f o r T* ( 1 3CO) from our T * ( 1 2 C O ) . Knapp et a l . (1976) observed both 1 2CO and 1 3CO i n Sharpless 222 at two p o s i t i o n s . The average r a t i o of t h e i r r a d i a t i o n temperatures i s f i v e . T h i s i n d i c a t e s that the temperature r a t i o f o r Sharpless 222 behaves much l i k e the other Sharpless regions s t u d i e d by Sewall (1980). T h e r e f o r e , we can estimate the magnitude and v a r i a t i o n of t h i s r a t i o f o r Shar p l e s s 222 using the r e s u l t s of other S h a r p l e s s regions from 42 Sewall (1980). The estimates are summarized i n Table I I . The r a t i o of T* ( 1 2CO) to T A ( 1 3CO) was l i n e a r l y i n t e r p o l a t e d f o r values w i t h i n a given range of T* ( 1 2 C O ) . Some s u b j e c t i v e assessments of the i n t e r p o l a t i o n were made a c c o r d i n g to the extent of the emission r e g i o n s . For l a r g e emission areas the r a t i o was u s u a l l y decreased by 0.1 to 0.2 and f o r very small areas of low emission the r a t i o was i n c r e a s e d by the same amounts. The estimates f o r the 1 3CO temperature are rough approximations. Extending t h i s method to i n d i v i d u a l sources such as S h a r p l e s s 222 should only be done as a l a s t r e s o r t . Data from 1 3CO o b s e r v a t i o n s are always p r e f e r a b l e . We b e l i e v e t h i s method has enabled us to estimate T* ( 1 3CO) to w i t h i n 25 per cent. The r e s u l t s of the peak T A ( 1 3CO) f o r -1.25 km s - 1 are i l l u s t r a t e d i n F i g u r e 9. T h i s contour p l o t c l e a r l y shows the hot spots embedded i n a c o o l e r background of 1 3CO emission. These r e s u l t s w i l l be d i s c u s s e d i n gr e a t e r d e t a i l in the next chapter. Using d e r i v e d values f o r T A ( 1 3 C O ) , we determined ?^( 1 3CO) from the standard formula, X ([hcd) =• ~ T h i s equation assumes that the 1 2CO and 1 3CO e x c i t a t i o n temperatures are equal. One expects t h i s to be approximately true but as we w i l l see t h i s may.not be v a l i d whenever there i s 43 a d i s t i n c t d i p i n the s p e c t r a l p r o f i l e . The en e r g i e s of the J=1 l e v e l s of the two isotope s p e c i e s are very n e a r l y e q u a l . The e x c i t a t i o n temperature f o r 1 2 C 0 i s probably l a r g e r and c l o s e r to the l o c a l gas k i n e t i c temperature than that of the o p t i c a l l y t h i n 1 3CO. T h i s i s due to the f a c t that there i s s i g n i f i c a n t r a d i a t i o n t r a p p i n g o c c u r i n g with the o p t i c a l l y t h i c k 1 2 C 0 l i n e . T h i s means that the 1 3 C 0 o p a c i t i e s c a l c u l a t e d with the formula above are a c t u a l l y lower l i m i t s of the r e a l v a l u e . The r e s u l t s T * ( 1 3C0) and f ( 1 3 C O ) are summarized i n Table VI f o l l o w i n g t h i s chapter. 4/4-T A ( 12C0) ( k e l v i n ) R a t i o ( i a C O ) / T ^ ( 1 3 C O ) >20 <3.5 16—20 4.0 — 3.5 10 — 1 6 5.0—4.0 <10 7.5 — 5.0 Table I I - T J ( 1 3 C O ) Generating Model Table I I d e t a i l s e stimates of the r a t i o T * ( 1 2 C O ) to T A ( 1 3 C O ) f o r d i f f e r e n t v a l u e s of T* ( 1 2 C O ) . These r e s u l t from an a n a l y s i s of data on Sha r p l e s s regions compiled by Sewall (1980). 4-5 10 ^0 0 r 10 0 l O C <n > H rH E-1 0 0 " \o° o c e e . \ \ \ \ 0 2 4 6 3 U R a t i o ( 1 2C0)/T A* ( 1 3C0) F i g u r e 8 -T* ( 1 3C0) Vs. T* ( 1 2CO)/T* ( 1 3C0) R a t i o s The r a t i o s were obtained from data of Sewall (1980). C i r c l e s are Sharpless 152 data, c r o s s e s are Sh a r p l e s s 206 data, and boxes are Shapless 148 data. T h i s r e s u l t was used to generate the T * ( 1 3 C 0 ) (see Table I I - T * ( , 3 C 0 ) Generating Model). 4-6 F i g u r e 9 -Generated T f t ( 1 3C0) Contours The T A ( 1 3CO) contours are generated from 1 2 C 0 o b s e r v a t i o n s . The contour u n i t s are 0.5 K st e p s . The d e c l i n a t i o n (DEC) verses r i g h t a scension (RA) p l o t shows the same f i v e CO hot spots present i n F i g u r e 7 ( T * ( 1 2CO) Con t o u r s ) . The u n i t s f o r both a x i s are arcminutes. The c e n t r e (0.0,0.0) i s , CX( 1 950 ) = 04 H26 M34 5.0 (Right Ascension) 6(1950) = 35d13'00'./0 ( D e c l i n a t i o n ) 47 48 III.5-Generated 1 3C0 Column D e n s i t i e s To o b t a i n an estimate f o r the 1 3C0 column d e n s i t y , N C O L ( 1 3 C O ) , we r e q u i r e v a l u e s f o r the h a l f power l i n e widths of the expected 1 3C0 p r o f i l e s . Since 1 3 C 0 was not observed in our survey we decided to study p a i r s of 1 2 C 0 and the corresponding 1 3 C 0 p r o f i l e s f o r other S h a r p l e s s r e g i o n s to determine i f there e x i s t s a r e l a t i o n s h i p between h a l f power l i n e widths f o r 1 2 C 0 and 1 3 C 0 p r o f i l e s . The r e s u l t s are given i n Table I I I . S152 and S148 r e f e r to two of the three S h a r p l e s s regions s t u d i e d by Sewall (1980). S222 and S239 are taken from Knapp et a l . (1976). The r a t i o , AV( 1 2CO) to A V ( 1 3 C O ) , adopted was 1.52 with a standard d e v i a t i o n of 0.10 i n any one measurement or an rms e r r o r of 0.04 i n the average. We found AV( 1 2CO) v i s u a l l y from our s p e c t r a l p r o f i l e s f o r each of the 89 p o s i t i o n s . To check the accuracy of t h i s method we assumed the best gaussian f i t to s i x of our p r o f i l e s chosen at random. The r e s u l t i n g AV( 1 2CO) from the gaussian p r o f i l e was found to be 20 ± 2 per cent l a r g e r than the v i s u a l l y measured h a l f widths. We decided to measure AV( 1 2CO) v i s u a l l y s i n c e a gaussian p r o f i l e was o b v i o u s l y not a good f i t f o r our data. The gaussians have wings that extend too f a r with a net r e s u l t of the gaussians becoming too wide i f the peak temperature of the observed p r o f i l e i s to be maintained. The a l t e r n a t i v e i s to reduce the width of the g a u s s i a n . U n f o r t u n a t e l y , t h i s a l s o reduces the peak temperature which was deemed unacceptable. A summary of the two methods i s given i n Table IV. Once AV( 1 2CO) was found v i s u a l l y , AV( 1 3CO) was determined 49 by d i v i d i n g each AV( 1 2CO) by the r a t i o of AV( 1 2CO) to A V ( 1 3 C O ) ( i . e . 1.52). The column d e n s i t y f o r 1 3C0, N C O L ( 1 3 C O ) , was c a l c u l a t e d using a r e l a t i o n d e r i v e d by M o r r i s as quoted i n Sewall (1980). where T e x ( 1 3 C O ) i s c a l c u l a t e d from, W J C 0 ) = T e x M=5.53 U [ l - T ; ( y o ) 3 t 0 , 3 3 j M o r r i s notes that the assumption T e y ( 13CO) =T e > < ( 1 2CO) must be used once more i n c a l c u l a t i n g the column d e n s i t y f o r 1 3CO. T h i s time the e r r o r i n c u r r e d i s i n the opposite sense as that i n t r o d u c e d i n the 1 3CO o p a c i t y c a l c u l a t i o n . Since T e x.( 1 3CO) and ^ ( ^ C O ) are m u l t i p l i e d together i n the column d e n s i t y e x p r e s s i o n the e r r o r i s s u b s t a n t i a l l y reduced. As long as Te/ ( 1 2CO) =. T e x ( 13CO) , which seems to be a reasonable assumption f o r S h a r p l e s s r egions, then the e r r o r s should very n e a r l y c a n c e l ; otherwise the N C O L( 1 3CO) estimate i s a lower l i m i t . F i g u r e 10 represents the column d e n s i t i e s . We b e l i e v e there are three w e l l r e s o l v e d c l o u d s : c l o u d # 1 , # 2 , and #3. They are l o c a t e d at Lk HCX101 ( 7 . 2 , - 1 0 . 8 ) , Lk H6X101 ( 0 . 0 , - 1 0 . 8 ) , and Lk HOH01 ( 7 . 2,-5.4) r e s p e c t i v e l y . Another two p o s s i b l e fragmentations were t r e a t e d i n t h i s p r o j e c t . Extreme care should be e x e r c i s e d s i n c e they are on the very l i m i t of our s p a t i a l 50 r e s o l u t i o n . Examination of the 1 2CO p r o f i l e s i n d i c a t e s these c l o u d s , #4 and #5, are probably r e a l . They are l o c a t e d at Lk HCX101 (3.6,-5.4) and Lk H«101 (0.0,-1.8). I t cannot be emphasized enough that the generated 1 3CO data i s only an approximation and should not be r e l i e d upon too h e a v i l y . The 1 2CO o b s e r v a t i o n s form the b a s i s of our observing program and as such are the very core of our c o n c l u s i o n s . A l l of our fragmentations appear r e a l on the 1 2CO g l o b a l p l o t s . 5 I Source P o s i t i o n AV(12C0) . AV( 1 3CO) R a t i o S152 W1S1 5.4 3.7 1.47 E1S1 5.0 3.2 1.55 S148 E0S1 3.9 2.8 1.40 S222 E0N0 4.0 2.7 1.49 E0N1 3.6 2.1 1.70 S239 E0N0 2.5 1.4 1.59 E2N0 1.6 1.0 1.46 a v e r a g e — 1.52 ± 0 . 0 4 (rms) Table III - P r o f i l e Half Width R a t i o s Our 1 3 C 0 p r o f i l e h a l f widths were c a l c u l a t e d u s ing the observed 1 2CO p r o f i l e h a l f widths. Data f o r four Sharpless r e g i o n s Knapp et a l . 1976, Sewall 1980) show the r a t i o of A V ( 1 2 C 0 ) to A V ( 1 3 C O ) i s remarkably c o n s t a n t . The A V ( 1 3 C O ) in our survey was determined by d i v i d i n g the measured A V ( 1 2 C 0 ) by the average r a t i o 1.52. 52 Parameter Method D e v i a t i o n between the two methods. V i s u a l Gaussian Veloc i t y D i r e c t l y from s p e c t r a l p l o t program, same as gaussian. <1% Standard d e v i a t i o n D i r e c t l y from s p e c t r a l p l o t program, same as gaussian. i l l sTL- 1 <1% AV{1JCO) V i s u a l e s t . AV-2U loqe2' cr 20 ± 2% high f o r gaussian Table IV - V e l o c i t y C a l c u l a t i o n s T h i s data summarizes the two approaches used to determine the v e l o c i t y of each p r o f i l e , the standard d e v i a t i o n of each p r o f i l e , and the p r o f i l e h a l f widths. D i f f e r e n c e s between v i s u a l i n s p e c t i o n and gaussian f i t t i n g r e s u l t e d only f o r values obtained f o r p r o f i l e h a l f widths. The value from the gaussian f i t i s high by about twenty per cent. T h i s i s due to the sharpness of the observed p r o f i l e shapes. Gaussian curves are much f l a t t e r than the observed p r o f i l e s and as a r e s u l t are poor r e p r e s e n t a t i o n s of the observed data. 53 F i g u r e 10 Generated N C O L ( 1 3 C O ) Contours The N C O L ( 1 3 C O ) contours are generated from 1 2CO o b s e r v a t i o n s . The contour u n i t s are 1 x 1 0 1 5 cm" 2. The d e c l i n a t i o n (DEC) versus r i g h t a s c e n s i o n (RA) p l o t shows the same f i v e CO hot spots present i n F i g u r e 7 ( T * ( 1 2CO) Con t o u r s ) . The u n i t s f o r both a x i s are arcminutes. To determine N t O L ( 1 3 C 0 ) , the r a t i o A V ( 1 2 C O ) to AV( 1 3CO) was found to be 1.52 +0.04 (see Table I l l - P r o f i l e Half Width R a t i o s ) . The c e n t r e (0.0,0.0) i s , Of ( 1 950) = 04*26*34*0 (Right Ascension) 6(1950) = 35°13'00'.'0 ( D e c l i n a t i o n ) 5 4 55 I I I . 6 - S t a r Counting Theory, Data And R e s u l t s The b a s i c procedure used here f o r s t a r counting i s that d e s c r i b e d by Dickman (1978). Enla r g e d p r i n t s and the o r i g i n a l s of the red and blue Palomar p r i n t s were used f o r the s t a r counts. The data from both sets of p r i n t s agreed. A tra n s p a r e n t g r i d of 'reseau' squares was p l a c e d on the p r i n t . The s i z e of the g r i d used was 1.8 arcminutes. T h i s i s the spacing between h a l f power p o i n t s of our t e l e s c o p e beam and a l s o the spacing used i n our map. A l l counts were made with the a i d of a low power microscope. A l l s t a r s i n a given square were counted without regard to t h e i r magnitudes. T h i s was adopted because the small g r i d s i z e would have introduced very l a r g e s t a t i s t i c a l u n c e r t a i n t i e s due to the small number of s t a r s i n each square with a p a r t i c u l a r magnitude. The s t a t i s t i c a l e r r o r expected with a count of 'n' s t a r s i n any square i s fr\ (Bok 1937). Star counting was performed twice f o r each of the blue and red p r i n t s . Star counts f o r the r e f e r e n c e f i e l d s were made i n each of the four c o r n e r s o u t s i d e the region of o b s c u r a t i o n . Both Palomar p r i n t s were used. The presence of any o b s c u r a t i o n i n the re f e r e n c e regions leads to a systematic underestimate of the e x t i n c t i o n i n the c l o u d . As a r e s u l t , c o n s i d e r a b l e care i s needed i n s e l e c t i n g the re f e r e n c e f i e l d to minimize the apparent o b s c u r a t i o n . Star counting i n each of the four corners was repeated f o r both c o l o u r s . The l i m i t i n g magnitude determined was 18.83 + 0.10 f o r the red p r i n t and 18.18 ± 0.25 f o r the blue p r i n t . 56 The number of stars counted in each square was averaged with adjacent values in order to obtain a more uniform d i s t r i b u t i o n consistent with the resolution of our CO contours. The weighted average of the star counts used had very l i t t l e e f f e c t on squares with one or more stars. In regions where no stars were counted a result was obtained from the smoothing of the immediate neighbours. This is probably more accurate than just assigning one star over each region without any stars, as was done by Dickman (1978). The weighting function used i s as follows: , , V + 3 . \ . J , / 3 l cen+recL on + ne s q u a r e / S+a.r Co ant - > \ 0 f i n t e r e s t / \ r • i \ " ' w ' o t m re.r e s t The weighted star counts for each grid element are then used to determine an e f f e c t i v e extinction. This was done u t i l i z i n g tables compiled by van Rhijn (1929). These tables contain smoothed values of the logarithm of the number of stars per square degree, brighter than an apparent photographic magnitude, m, and given in ten degree steps of galactic longitude. The table actually used for th i s work i s contained in Allen's "Astrophysical Quantities". Van Rhijn's tables have long been in question. Considerable corrections had to be used to reconcile the dif f e r e n t magnitude systems in the star catalogues used in his compilations. Unfortunately, these tables remain the only source of 57 i n f o r m a t i o n f o r general s t a r counts. Van R h i j n ' s t a b l e s give l o g N as a f u n c t i o n of the o l d photographic magnitude. Here N r e f e r s to the number of s t a r s counted per square degree at a s p e c i f i c g a l a c t i c l o n g i t u d e . The o l d photographic magnitude i s very n e a r l y the same as the modern blue magnitudes. In reducing the blue counts from the Palomar p r i n t s we simply used the t a b l e a d j u s t e d f o r a g a l a c t i c l a t i t u d e of -9.0 degrees. The i n t e r p o l a t e d r e s u l t s from A l l e n are given in Table V. If one counts the number of s t a r s per square degree i n the refe r e n c e r e g i o n , one may a s s i g n a l i m i t i n g magnitude, m ( r e f ) , to these counts. If at some p o i n t i n s i d e the c l o u d one repeats the same procedure then the corresponding magnitude, m(pt), should be l e s s than m ( r e f ) . T h i s means fewer s t a r s are seen through the obscur i n g c l o u d . The e x t i n c t i o n at that p o i n t i s then, A(pt) = m(ref) - m(pt) magnitudes i n the blue. Since van Rh i j n ' s t a b l e s are only v a l i d f o r blue magnitudes we have to f i n d a s i m i l a r approach f o r the red p r i n t . An important property of the van R h i j n t a b u l a t i o n s i s t h e i r near l i n e a r i t y c l o s e to the g a l a c t i c plane. T h e r e f o r e , we can w r i t e l o g N(mfe) =a 6 + b 6m 6. Dickman (1978) c o n s i d e r s a s e r i e s s o l u t i o n fo r the corresponding r e l a t i o n s h i p f o r red magnitudes ( i . e . l o g N(m^) = a f t + b^m^ + c f tm K 2 +...). To the f i r s t order he f i n d s that c^ = 0 and b^ = b f i. T h e r e f o r e , one can t r e a t the red magnitudes i n e x a c t l y the same manner as the blue magnitudes. For the blue magnitudes we have 58 where b f t = 0.35 from van R h i j n . For the red magnitudes we have s i n c e = b f t = 0.35. The f i n a l s tep i s the r e d u c t i o n of the two c o l o u r magnitudes to some standard c o l o u r magnitude. I t i s c o n v e n t i o n a l to take V = 5500 angstroms as the standard v i s u a l wavelength. A l l converted e x t i n c t i o n s are termed v i s u a l e x t i n c t i o n s , A v. Reduction to v i s u a l e x t i n c t i o n s i s made by assuming a 'standard' i n t e r s t e l l a r reddening law. The conver s i o n f a c t o r s r e l a t i n g red and blue magnitudes to v i s u a l are given below (Dickman 1978). A „ * 0.1b A 6 I 8 s 4 3 0 0 A A . I.3LI A «« "~ 6 5 0 0 A The 'standard' reddening law has been suspect f o r q u i t e some time. The p o s s i b l e d e v i a t i o n s are d i s c u s s e d i n d e t a i l i n Dickman's t h e s i s (1976). Once the v i s u a l e x t i n c t i o n was determined f o r each c o l o u r , intercomparison was p o s s i b l e . For our c l o u d we found the f e a t u r e s present on the red and blue e x t i n c t i o n contour maps to agree f a i r l y w e l l . The magnitude of the red e x t i n c t i o n d i s a g r e e s 59 s i g n i f i c a n t l y from the blue only f o r l a r g e e x t i n c t i o n s (A >, 3.5). The v i s u a l e x t i n c t i o n d e r i v e d from the red p r i n t became i n c r e a s i n g l y higher than that f o r the blue s t a r counts as A v i n c r e a s e d above 3.5 magnitudes. Since the red Palomar p r i n t had on average more s t a r s per g r i d element the e x t i n c t i o n s determined from the red p r i n t s f o r A >, 3.5 are probably more r e p r e s e n t a t i v e of the true value than those obtained from the blue p r i n t . The o v e r a l l u n c e r t a i n t y i n A v f o r regions where s t a r s were counted i s probably no more than one magnitude. The areas of great e r e x t i n c t i o n are a lower l i m i t where the u n c e r t a i n t y i s s e v e r a l magnitudes. The squares encompassing the HII region are p a r t i c u l a r l y d i f f i c u l t to judge s i n c e no s t a r s can be d i s t i n g u i s h e d i n the exposed areas of the Palomar p r i n t s . A f u r t h e r problem that should be r e c o n c i l e d i s the expected number of foreground s t a r s t hat were counted. From the s t a r counts on the blue p r i n t we found no evidence f o r the presence of more than one foreground s t a r per g r i d element. Since Sharpless 222 i s l o c a t e d o f f the g a l a c t i c plane and 800 parsecs d i s t a n t we expect few foreground s t a r s as i n d i c a t e d by the blue s t a r counts. S u b t r a c t i n g one s t a r per g r i d element throughout the f i e l d w i l l change the r a t i o between the number of s t a r s i n the r e f e r e n c e region and the number of s t a r s i n the obscured region by a small amount. T h i s leads to a s l i g h t underestimate of the a c t u a l e x t i n c t i o n . In c o n c l u s i o n , we f e e l c o n f i d e n t that the e x t i n c t i o n s are lower l i m i t s a c c u r a t e to one magnitude, except i n regions where no s t a r s were found i n a g r i d element. Table VI g i v e s a summary of the r e s u l t s of t h i s chapter. 60 Table V -Van R h i j n ' s Table f o r b = -9.0" The l o g a r i t h m of the number of s t a r s of a l l magnitudes per square degree to a l i m i t i n g magnitude, m, i s given under the heading l o g N m. T h i s data i s i n t e r p o l a t e d f o r b = -9.0° from A l l e n ' s " A s t r o p h y s i c a l Q u a n t i t i e s " . 61 Table V -Van R h i j n ' s Table f o r b=-9.0° m l o g N m m l o g N m m l o g N m 12.0 1.63 14.4 2.62 16.8 3.49 12.1 1.67 14.5 2.66 16.9 3.52 12.2 1.71 14.6 2.70 17.0 3.56 12.3 1.76 14.7 2.74 17.1 3.59 12.4 1.80 14.8 2.78 17.2 3.63 12.5 1.84 14.9 2.82 17.3 3.66 12.6 1.88 15.0 2.86 17.4 3.70 12.7 1.92 15.1 2.89 17.5 3.73 12.8 1.97 15.2 2.93 17.6 3.77 12.9 2.01 15.3 2.96 17.7 3.80 13.0 2.05 15.4 3.00 17.8 3.84 13.1 2.09 15.5 3.03 17.9 3.87 13.2 2.13 15.6 3.07 18.0 3.90 13.3 2.17 15.7 3.10 18.1 3.94 13.4 2.21 15.8 3.14 18.2 3.98 13.5 2.26 15.9 3.17 18.3 4.01 13.6 2.30 16.0 3.21 18.4 4.05 13.7 2.34 16.1 3.. 24 18.5 4.09 13.8 2.38 16.2 3.28 18.6 4.13 13.9 2.42 16.3 3.31 18.7 4.17 14.0 2.46 16.4 3.35 18.8 4.20 14.1 2.50 16.6 3.38 18.9 4.24 14.2 2.54 16.7 3.42 19.0 4.28 14.3 2.58 16.8 3.45 F i g u r e s 11, 12, and 13 A 6, A R, and A v E x t i n c t i o n Contours The magnitudes of e x t i n c t i o n were determined using the standard procedure o u t l i n e d i n s e c t i o n I I I . 6 - S t a r Counting Theory, Data, and R e s u l t s . The numbers on each contour map represent the i n t e r v a l of e x t i n c t i o n . For example, a 4 would i n d i c a t e the e x t i n c t i o n i s between 3 and 4 magnitudes. F i g u r e 11 rep r e s e n t s the r e s u l t s from the blue (B=4300 A) p r i n t of the Palomar Survey. F i g u r e 12 giv e s the r e s u l t s from the red p r i n t (R= 6500 A) and Fig u r e 13 i s the average of the preceeding f i g u r e s converted to v i s u a l e x t i n c t i o n (VS5500 A). The con v e r s i o n procedure i s o u t l i n e d i n Dickman (1978). The dashed regions represent the extent of the n e b u l o s i t y as seen on each of the Palomar p r i n t s . The a x i s are s c a l e d i n 1.8 arcminute i n t e r v a l s from the c e n t r e (0.0,0.0), 0((1950) = 04 H26 M34. S0 (Right Ascension) 6(1950) = 35°13'00"0 ( D e c l i n a t i o n ) F i g u r e 11 -A 6 E x t i n c t i o n Contours F i g u r e 13 -A„ E x t i n c t i o n Contours G 6 Table VI -Data Summary Column 1 g i v e s the c o o r d i n a t e s of each o b s e r v a t i o n . (x.x,y.y) means x.x arcminutes r i g h t a s c e n s i o n and y.y arcminutes d e c l i n a t i o n from our nominal c e n t r e , (XO950) = 0 4 H 2 6 M 3 4 f u (Right Ascension) 8 (1950) = 35°13'oo'.'o ( D e c l i n a t i o n ) Column 2 i s the observed peak 1 2CO r a d i a t i o n temperature (K) and column 3 g i v e s the corres p o n d i n g L.S.R. v e l o c i t y (km s ~ 1 ) . Column 4 g i v e s the 1 2CO e x c i t a t i o n temperature (K). Columns 5 and 6 gi v e the expected 1 3CO p r o f i l e h a l f widths (km s" 1) and r a d i a t i o n temperature (K). The l a s t two columns give the expected 1 3CO o p a c i t y (nepers) and the generated 1 3CO column d e n s i t y , N 1 3 ( X 1 0 1 4 cm' 2). A l l of the c a l c u l a t i o n s are d e s c r i b e d f u l l y i n chapter I I I . Table VI -Data Summary Position mi 2 A V rn 1 2 ex AV1 3 ml J 1 A, L 1 1 N 1 3 (0.0,-14.4) 8.5 -1.0 11.9 1.9 1.2 0.15 27 (0.0,-12.6) 14.1 -0.9 17.6 2.1 3.0 0.23 89 (-10.8,-10.8) 12.8 -2.5 16.3 1.9 2.6 0.22 67 (-9.0,-10.8) 14.1 -1.3 17.5 2.2 2.9 0.23 93 (-5.4,-10.8) 14.6 -1.8 18.1 2.5 3.1 0.24 120 (-1.8,-10.8) 17.1 -2.0 20.6 2.6 4.3 0.29 190 (1.8,-10.8) 13.3 -1.1 16.7 2.5 2.8 0.24 99 (5.4,-10.8) 17.2 -0.6 20.7 2.4 4.3 .0.29 170 (7.2,-10.8) 20.8 -0.7 24.3 2.4 6.3 0.36 290 (9.0,-10.8) 14.2 -0.7 17.6 3.5 3.0 0.24 160 (10.8,-10.8) 11.5 -1.6 14.9 2.2 2.3 0.22 69 (-9.0,-9.0) 11.5 -1.5 14.9 2.6 2.3 0.22 80 (0.0,-9.0) 15.9 -1.2 19.4 2.3 3.7 0.27 130 (9.0,-9.0) 14.8 -1.0 18.3 2.0 3.2 0.24 97 (-7.2,-7.2) 10.4 -1.5 13.8 2.1 1.9 0.20 49 (0.0,-7.2) 17.5 -1.3 21.0 1.6 4.4 0.29 120 (3.6,-7.2) 14.2 -2.4 17.6 3.1 3.0 0.24 140 (5.4,-7.2) 15.9 -1.4 19.4 2.7 3.7 0.27 160 (7.2,-7.2) 15.4 -1.0 18.8 2.9 3.4 0.25 150 (9.0,-7.2) 14.8 -1.6 18.3 2.5 3.2 0.24 120 (-5.4,-5.4) 10.1 -1.5 13.5 2.0 1.8 0.20 46 (0.0,-5.4) 13.6 -1.0 17.1 2.3 2.8 0.23 95 (3.6,-5.4) 18.9 -1.0 22.4 2.1 5.3 0.33 190 (5.4,-5.4) 13.9 -1.1 17.4 2.8 3.0 0.25 120 P o s i t ion r n i 2 A V m i ! e* A V1 3 rp 1 3 1 A /£. 1 3 N X 3 (7.2,-5.4) 20.9 -1.0 24.3 1.7 6.3 0.36 210 (9.0,-5.4) 13.1 -1.3 16.5 2.0 2.8 0.24 78 (-9.0,-3.6) 12.5 -2.5 15.9 1.8 2.5 0.22 63 (-3.6,-3.6) 11.8 -1.9 15.2 1.9 2.3 0.22 54 (0.0,-3.6) 15.2 -0.9 18.6 2.3 3.4 0.25 120 (3.6,-3.6) 11.3 -2.0 14.7 2.8 2.2 0.22 82 (5.4,-3.6) 13.5 -1.4 16.9 2.2 2.9 0.24 91 (7.2,-3.6) c.12.0 -1.5 15.4 2.4 2.4 0.22 77 Bad Po i n t (9.0,-3.6) 12.2 -1.6 15.6 2.0 2.4 0.22 67 (10.8,-3.6) 12.6 -1.6 16.0 1.7 2.5 0.22 59 (-9.0,-1.8) 11.5 -1.8 15.0 1.6 2.2 0.21 47 (-1.8,-1.8) 10.5 -2.1 13.9 2.2 2.0 0.21 54 (0.0,-1.8) 17.2 -1.3 20.7 2.1 4.2 0.28 150 (1.8,-1.8) 8.2 -1.1 11.5 1.4 1.5 0.20 25 (3.6,-1.8) 12.0 -2.1 15.4 2.1 2.4 0.22 68 (5.4,-1.8) 13.8 -1.0 17.2 2.4 3.0 0.25 110 (7.2,-1.8) 13.1 -1.2 16.5 2.4 2.8 0.24 95 (9.0,-1.8) 15.8 -1.0 19.2 2.1 3.7 0.27 120 (-12.6,0.0) 10.0 -0.6 13.4 1.0 1.8 0.20 23 (-10.8,0.0) 7.7 -1.8 11.1 1.6 1.3 0.19 25 (-9.0,0.0) 11.1 -3.5 14.5 1.6 2.2 0.22 46 (-7.2,0.0) 12.7 -2.1 16.2 2.3 2.7 •0.23 85 (-5.4,0.0) 2.9 -1.3 6.1 1.0 0.5 0.19 6 (-3.6,0.0) 14.5 -1.9 18.0 1.8 3.1 0.24 81 (-1.8,0.0) 8.6 -2.3 11.9 2.5 1.6 0.20 46 (0.0,0.0) 9.9 -2.1 13.3 2.3 1.9 0.22 55 P o s i t i o n m i 2 1 A V m i 2 1 ex AV 1 3 m i 3 1 A ^-1 3 N 1 3 (1.8,0.0) 14.0 -1.9 17.5 2.4 2.9 0.23 100 (3.6,0.0) 12.3 -0.5 15.7 2.1 2.5 0.22 70 (5.4,0.0) 11.1 -2.2 14.5 2.5 2.2 0.22 72 (7.2,0.0) 11.3 -1.1 14.8 2.8 2.2 0.22 84 (9.0,0.0) 12.8 -0.8 16.2 2.4 2.6 0.23 85 (10.8,0.0) 11.0 -2.5 14.4 2.2 2.1 0.21 59 (12.6,0.0) 7.4 -0.9 10.8 2.3 1.2 0.18 31 (-1.8,1.8) 9.6 -1.3 13.0 2.8 1.8 0.21 63 (0.0,1.8) 7.6 -1.0 11.0 1.5 1.3 0.19 23 (1.8,1.8) 9.6 -1.7 13.0 2.0 1.8 0.20 43 (-3.6,3.6) 11.0 -2.1 14.4 2.1 2.1 0.22 59 (0.0,3.6) 7.5 -1.7 10.8 2.0 . 1.3 0.19 30 (3.6,3.6) 9.6 -2.2 13.0 1.7 1.8 0.21 37 (5.4,3.6) 10.1 -1.1 13.5 1.9 2.0 0.22 46 (7.2,3.6) 13.7 -0.2 17.1 1.1 2.9 0.24 44 (-9.0,5.4) 12.4 -1.2 15.8 1.7 2.5 0.23 58 (-5.4,5.4) 13.2 -0.9 16.6 2.0 2.8 0.23 77 (-1.8,5.4) 11.4 -1.4 14.8 1.4 2.3 0.22 44 (0.0,5.4) 9.7 -1.3 13.1 2.2 1.8 0.21 49 (1.8,5.4) 5.6 -1.1 8.9 1.5 0.9 0.17 15 (5.4,5.4) 11.1 -1.7 14.5 1.7 2.2 0.22 50 (9.0,5.4) 13.0 -1.0 16.4 2.0 2.7 0.23 75 (-7.2,7.2) 12.0 -2.0 15.4 1.7 2.4 0.23 55 (0.0,7.2) 15.1 -1.1 18.6 1.4 3.3 0.25 68 (5.4,7.2) 13.9 -1.4 17.4 1.7 2.9 0.23 74 (7.2,7.2) 13.1 -2.3 16.5 1.8 2.7 0.23 69 P o s i t i o n rp 1 2 1 A V r p l 2 ex AV 1 3 rp l 3 A 3 N 1 3 (-9.0,9.0) 6.4 -1.5 9.8 1.5 0.9 0.15 14 (0.0,9.0) 11.6 -1.2 15.1 2.0 2.3 0.22 63 (9.0,9.0) 13.2 -1.9 16.. 7 2.2 2.7 0.23 84 (-10.8,10.8) 5.4 -2.1 8.7 1.2 0.7 0.15 9 (-9.0,10.8) 7.8 -1.1 11.2 1.0 1.1 0.16 13 (-5.4,10.8) 10.0 -0.6 13.4 1.9 1.7 0.18 39 (-1.8,10.8) 10.6 -2.0 14.0 1.2 1.9 0.20 30 (0.0,10.8) 9.5 -2.1 12.9 2.5 1.6 0.18 48 (1.8,10.8) • 7.6 -0.9 11.0 2.0 1.1 0.16 26 (7.2,10.8) 8.5 -0.8 11.9 1.6 1.4 0.17 25 (9.0,10.8) 13.3 -1.2 16.7 2.2 2.7 0.23 84 (0.0,12.6) 5.6 -1.2 8.9 1.7 0.7 0.14 14 71 IV. DISCUSSION OF RESULTS  I V . 1 . 1 - P r e v i o u s Observations: I n t r o d u c t i o n Sharpless 2 2 2 appears to have been observed f i r s t by F.G. Pease ( 1 9 1 7 ) as NGC 1 5 7 9 Perseus. A general d e s c r i p t i o n and the l o c a t i o n was given. Hubble ( 1 9 2 2 ) c a t a g o r i z e d NGC 1 5 7 9 as an obj e c t of s i z e two on a s c a l e i n c r e a s i n g i n s i z e from one to f i v e . Herbig ( 1 9 5 6 ) suggested Lk H O U 0 1 as the probable source of i l l u m i n a t i o n f o r NGC 1 5 7 9 . The photographic magnitude of Lk HCV101 i s 1 7 . Herbig noted that there i s a disc r e p a n c y of nine magnitudes between the observed b r i g h t n e s s and that given by Hubble's r e l a t i o n connecting the apparent magnitude of the e x c i t i n g s t a r and dimensions of the nebula. He c o r r e c t l y e x p l a i n e d that t h i s problem was a r e s u l t of dark lanes of m a t e r i a l superimposed on the i l l u m i n a t i n g s t a r , Lk H C X 1 0 1 . The name Sharpless 2 2 2 i s d e r i v e d from a l i s t of HII regions compiled by S. Sha r p l e s s ( 1 9 5 9 ) . In t h i s catalogue Sharpless 2 2 2 i s d e s c r i b e d as a very b r i g h t i r r e g u l a r HII region with diameter s i x arcminutes. The l o c a t i o n i s a l s o given. Palomar Sky Survey p r i n t s of the region show Sharpless 222 as a small b r i g h t nebula, c r o s s e d by s e v e r a l o b s c u r i n g dark l a n e s . I t l i e s 'on the edge of a very long and narrow dust l a n e . As d e s c r i b e d by the ' B l i s t e r ' Model ( I s r a e l 1977, Gilmore 1978: r e f e r r e d to i n the INTRODUCTION), t h i s c o n f i g u r a t i o n of s t a r formation i s f a i r l y common. There are four components present i n Sharpless 222: the e x c i t i n g s t a r , the HII r e g i o n , the HI r e g i o n , and the molecular c l o u d and our s p a t i a l r e s o l u t i o n i s capable of r e s o l v i n g only the l a t t e r two. The f i r s t two components are 72 t r e a t e d b r i e f l y i n t h i s s e c t i o n . The s p e c t r a l type of the e x c i t i n g s t a r , Lk H0O01, has been a matter of debate ever s i n c e Herbig (1956) c l a s s i f i e d the obj e c t as an F type s t a r . In the l a s t ten years most data have i n d i c a t e d that the s p e c t r a l type i s probably that of a zero age main sequence (Z.A.M.S.) BO.5 s t a r ( A l l e n 1973, Brown et a l . 1976, A l t e n h o f f et a l . 1976, H a r r i s 1976), where a Z.A.M.S. BO.5 type s t a r i s d e f i n e d a c c o r d i n g to the parameters given by Panagia (1973). The photographic magnitude of mp3 = 17 and the d i s t a n c e of at l e a s t 800 parsecs (Herbig 1971) i n d i c a t e s there are n e a r l y ten magnitudes of v i s u a l e x t i n c t i o n p r e s e n t . The spectrum of the po i n t source f o r Lk HGX101 above 5 GHz has a s p e c t r a l index of one (S/* V 1,"Cohen 1980) with some f l a t t e n i n g of the spectrum between 30 and 90 GHz (Schwartz and Spencer 1977). The o p t i c a l spectrum i s continuous (Cohen and Kuhi 1979) and from the r a t i o of hydrogen l i n e s P (3 (Thompson et a l . 1977) to H/ (Cohen and Kuhi 1979), Cohen (1980) f i n d s Av = 10 magnitudes. For the p o i n t source Cohen (1980) a l s o c a l c u l a t e s a mass l o s s of 3x1 0 - 5 M& yr ~ 1 which corresponds w e l l with a B0.5 Z.A.M.S. s t a r . Cohen (1980) uses s e v e r a l methods to determine the v i s u a l e x t i n c t i o n . In each case he f i n d s the t o t a l e x t i n c t i o n of the s t a r to be between 9 and 10 magnitudes c o n s i s t e n t with a B0.5 s t a r . Lk HCX101 i s a b r i g h t i n f r a r e d source e x c i t i n g the surrounding nebula NGC 1579 (Cohen and Woolf 1971). Cohen and Dewhirst (1970) found Lk HCX101 c o i n c i d e n t with the i n f r a r e d source IRC 40091 (Neugebauer and Leighton 1969). The K magnitude appears to be near three (Grasdalen and Gaustad 1971, A l l e n 73 1973, S t r e c k e r and Ney 1974) with a c o l o u r index I - K of 5.72 magnitudes (Cohen and Dewhirst 1970). The observed i n f r a r e d excess and r i c h emission l i n e spectrum p r o v i d e s evidence f o r both a gas and dust envelope surrounding Lk Hon 01. On an unpublished p r i n t of the Steward Observatory Near I n f r a r e d Photographic Sky Survey there are about a dozen s t a r s i n the molecular c l o u d with at l e a s t a 2.5 magnitude c o l o u r excess. Of these, ten are w i t h i n our f i e l d of o b s e r v a t i o n s . Table VII g i v e s a summary of t h e i r p o s i t i o n s and any c o i n c i d e n c e with the CO o b s e r v a t i o n s . F i g u r e 14 i s a diagram of the Steward Observatory i n f r a r e d p r i n t . Lk HCX101 can thus be represented as a BO.5 s t a r i n an e a r l y phase of e v o l u t i o n . I t seems to be l o s i n g mass at a r a t e of about 3 x 10~ 5 M<2> y r _ 1 . The evidence of mass l o s s r a ther than mass i n f a l l i m p l i e s that the p r o t o s t a r i s no longer c o l l a p s i n g . In a l l p r o b a b i l i t y i t has very r e c e n t l y reached the main sequence. As a r e s u l t of the mass l o s s , a t h i c k c i r c u m s t e l l a r dust s h e l l has formed around Lk Hon 01 (Simon and Dyck 1977, Cohen 1980). The dust s h e l l i s most l i k e l y r e s p o n s i b l e f o r producing both the high reddening and the i n f r a r e d excesses p r e s e n t . I t appears that the dust and HII regions are clumped i n an asymmetric way with the HII re g i o n at the core (Thompson et a l . 1976, Thompson and Reed 1976). The s h e l l geometry permits only two per cent of the s t e l l a r i o n i z i n g photons to escape, c r e a t i n g a weakly i o n i z e d h a l o . The t o t a l e x t i n c t i o n a r i s i n g from t h i s c i r c u m s t e l l a r s h e l l i s about 9 to 10 magnitudes. For a B0.5 s t a r at 800 parsec s , Osterbrook (1974, Table 2.3) suggests an inner i o n i z e d r e gion of 0.7 arcseconds and a more extended 74 zone of emission (32 a r c s e c o n d s ) . These r a d i i do agree f a i r l y w e l l with the observed r a d i o p i c t u r e . Spencer and Schwartz (1974) estimated the inner core was l e s s than one arcsecond. A l t e n h o f f et a l . (1976) and H a r r i s (1976) both narrowed the inner core s i z e to 0.5 arcseconds. H a r r i s f u r t h e r notes the e x i s t e n c e of the more extended emission and A l t e n h o f f et a l . (1976) g i v e s the s i z e as 35 arcseconds based on the 5 and 10.7 GHz data. The q u e s t i o n of the asymmetry of the nebula can be so l v e d by assuming that the HII region i s f l a t t e n e d . Herbig (1971) suggested that the a s s o c i a t e d nebula might i n f a c t be e l l i p t i c a l i n shape and have three p a r t s obscured. Cohen (1980) suggests that the c i r c u m s t e l l a r dust a c t u a l l y l i e s i n a f l a t t e n e d d i s t r i b u t i o n , t h i n n e s t over the pole s of Lk HOM01. In t h i s way only a small f r a c t i o n of the s t e l l a r f l u x can escape through the p o l a r caps. T h i s appears to be the case with the s t e l l a r r a d i a t i o n . T h i s f l u x h e l ps maintain the o p t i c a l nebula, NGC 1579, and the observed r a d i o h a l o . The youth of the i l l u m i n a t i n g s t a r , Lk H&101, i s supported by the e a r l y s p e c t r a l type, the high i n f r a r e d excesses and the high mass l o s s observed. Lk Hon 01 appears to be an e x c e l l e n t candidate with which strong CO emission w i l l be a s s o c i a t e d . 75 I n f r a r e d Star 1 2 C 0 contours ( k e l v i n ) A, ext i n c . (mag.) 1 3 CO contours ( k e l v i n ) N C 0 L( 1 3C0) contours ( x l O 1 5 cm 2) #1-(13.4,5.5) 10.0 0.8 2.8 8.0 #2-(5.7,-13.1) 10.0 2.2 2.3 6.0 #3-(-2.7,-6.6) 8.5 2.2 2.8 6.0 #4-(-7.0,1.6) 14.0 2.0 3.3 12.5 #5-(-3.0,6.7) 9.0 1.9 2.8 6.0 #6-(2.2,-1.8) 5.0 1.5 1.8 4.0 #7-(3.8,-4.5) 13.0 1.8 4.5 14.0 #8-(3.5,-4.2) 12.0 1.7 4.0 11.0 #9-(4.1,-3.5) 11.5 1.6 2.8 10.0 #10-(4.9,-3.1) 12.5 1.6 2.8 9.0 #ll-(5.6,-3.8) 12.5 2.0 2.8 10.0 Table VII - I n f r a r e d Star P o s i t i o n s The eleven i n f r a r e d s t a r s are l i s t e d with t h e i r p o s i t i o n s from the c e n t r e of our o b s e r v a t i o n f i e l d . CV(1950) = 04 H26 n34. S0 (Right Ascension) £(1950) = 35°13'00['0 ( D e c l i n a t i o n ) A l s o given are the 1 2CO r a d i a t i o n temperatures, v i s u a l e x t i n c t i o n , expected 1 3CO r a d i a t i o n temperatures, and the generated 1 3CO column d e n s i t y f o r each of the i n f r a r e d s t a r p o s i t i o n s . Very l i t t l e c o i n c i d e n c e between the p o s i t i o n s of the CO hot spots and the i n f r a r e d s t a r s can be seen. 76 F i g u r e 14 - I n f r a r e d Diagram F i g u r e 14 i s a schematic r e p r e s e n t a t i o n of the i n f r a r e d o p r i n t (8000 to 9000 A) reproduced by kind p e r m i s s i o n from Dr. E. C r a i n e of the Steward Observatory. The converging arrows i n d i c a t e s the c e n t r e of our survey f i e l d , 0(0950) = 0 4 M 2 6 M 3 4 f o (Right Ascension) 6(1950) = 35 °13'00!'0 ( D e c l i n a t i o n ) Lk H0U01 i s i n d i c a t e d by LH101 and the other i n f r a r e d s t a r s i n our o b s e r v a t i o n f i e l d are numbered. The d e t a i l s of each are summarized in Table V I I - I n f r a r e d S t a r P o s i t i o n s . The s c a l e of the f i g u r e i s 7.03 m i l l i m e t r e s per 1.8 arcminute i n t e r v a l . 77 / / I Figure 14 - I n f r a r e d Diagram 6 I 9 ' / / \ \ 78 IV. 1 . 2-Previou,s O b s e r v a t i o n s : HI R e s u l t s The f i r s t twenty-one centimeter data of Sharpless 222 were obtained by R i e g e l (1967). He de t e c t e d an HI f e a t u r e which c o i n c i d e s e x a c t l y with Lk HCX101. He found a systematic r a d i a l v e l o c i t y of 3.5 km s~ 1 and a v e l o c i t y h a l f width of 8.1 km s _ 1 . An incomplete map of HI was obtained by F e l l i and Churchwell (1972). They found a maximum main beam b r i g h t n e s s temperature of one k e l v i n . The peak HI temperature was l o c a t e d p r e c i s e l y at the o p t i c a l c o o r d i n a t e s . The p a r t i a l l y sampled map i s given i n F i g u r e 15. The most complete HI data yet obtained i s that of Dewdney and Roger (1981). An example of t h e i r s p e c t r a i s given i n F i g u r e 16. The data were obtained using the s y n t h e s i s i n t e r f e r o m e t e r at the Dominion Radio A s t r o p h y s i c a l Observatory, P e n t i c t o n , B r i t i s h Columbia. The s p e c t r a show two components i n HI. The v e l o c i t y of the a b s o r p t i o n component, 0 ± 2 km s _ 1 , c o i n c i d e s very w e l l with the observed d i p i n our 1 2CO p r o f i l e s ( F igure 18). The ab s o r p t i o n component i s present i n a l l the s p e c t r a provided by Dewdney and Roger. From these s p e c t r a we see no evidence of v e l o c i t y s t r u c t u r e o u t s i d e the c e n t r a l p r o f i l e . F i g u r e 17 i s a three dimensional d i s p l a y of t h e i r HI data. The f r o n t face i s a map of the i n t e g r a t e d HI with the p o s i t i o n of Lk H0r*lO1 i n d i c a t e d . As we can see Lk HO<101 i s l o c a t e d about three arcminutes to the east of the hig h e s t HI contour c e n t r e . The two other faces i n d i c a t e the HI v e l o c i t y s t r u c t u r e f o r constant r i g h t ascension or d e c l i n a t i o n . Note that the s p a t i a l r e s o l u t i o n used at P e n t i c t o n i s s i m i l a r to our 1 2 C 0 r e s o l u t i o n 79 f o r S h arpless 222. A f u l l comparison of the two data s e t s i s given i n s e c t i o n IV.2. 80 an F i g u r e 15 -HI Contour Map, F e l l i and Churchwell T h i s HI contour map of S h a r p l e s s 222 i s the r e s u l t of incomplete survey by F e l l i and Churchwell (1972). The r a d i o and o p t i c a l c o o r d i n a t e s c o i n c i d e . T h i s i s i n d i c a t e d as the c r o s s . The contour i n t e r v a l i s 0.2 K g i v i n g a peak b r i g h t n e s s temperature of one k e l v i n . 81 ' 1 20 10 0 -10 -20 V(km-sec" 1 ) F i g u r e 16 -HI P r o f i l e , Dewdney and Roger (1981) T h i s i s a r e p r e s e n t a t i v e HI p r o f i l e from Dewdney and Roger (1981). The f i g u r e shows the two component s p e c t r a l f i t s . T h i s s p e c t r a i s t h a t of Lk H&101 (5.4,-3.6). The i n d i v i d u a l components i n emission and a b s o r p t i o n are shown in l i g h t l i n e s , and the f i t t e d r e s u l t i n heavy l i n e s superimposed on the measured spectrum. The r e s i d u a l i s shown below. 8 2 4*27" 4*26m Right A s c e n s i o n F i g u r e 17 -3-D Synopsis of the HI r e s u l t s T h i s i s a three dimensional r e p r e s e n t a t i o n of the HI emission a s s o c i a t i o n with Sharpless 222. The shaded contours show HI emission i n t e g r a t e d over the v e l o c i t y range -6 to +10 km s _ 1 . The contour steps correspond to i n t e r v a l s of 1.5 x 102° cm - 2 i n column d e n s i t y . Superimposed i s a contour map of continuum emission showing the source a s s o c i a t e d with Lk H£X101 (white s t a r ) . Contour l e v e l s are 20, 70, 120 and 170 m i l l i j a n s k y . The s y n t h e s i z e d beam i s shown i n the lower r i g h t c o r n e r . Coordinates are f o r epoch 1950. The s i d e p r o j e c t i o n s are i n t e g r a t e d over the f u l l r i g h t ascension (RA) and d e c l i n a t i o n (DEC) ranges d i s p l a y e d on the f r o n t f a c e . (Dewdney and Roger 1981). 83 IV.1.3-Previous Observations: CO R e s u l t s As we have i n d i c a t e d i n s e c t i o n IV. 1 .1 Lk H&101 appears to be a young and very luminous s t a r . CO emission, along with other molecular emission and masers, g e n e r a l l y i n d i c a t e s r e g i ons of ongoing s t a r formation. As a consequence one expects the region around Lk Hon 01 to be a good source of CO emission. To date no OH or H aO masers have been d e t e c t e d i n the Lk H6X101 v i c i n i t y (Turner 1971, B l i t z and Lada 1979). 1 2C0 emission i n Sharpless 222 was f i r s t d e t e c t e d by Wilson et a l . (1973). Only one spectrum was taken. They found an extended source (2 arcminutes) with a c e n t r a l v e l o c i t y of 0 ± 2 km s - 1 . The p r o f i l e h a l f width was rather l a r g e , 7 ± 2 km s - 1 . The peak antenna temperature was 1.5 ± 0.3 K. They a l s o noted the presence of 1 2CO emission in the wings of t h e i r p r o f i l e . The v e l o c i t y of t h i s f e a t u r e was +12 km s - 1 . The f i r s t survey of S h a r p l e s s 222 with 1 2CO was done by Knapp et a l . (1976). Two p o s i t i o n s were a l s o observed i n 1 3CO. The region s t u d i e d corresponds to only a very small s e c t i o n of our survey c e n t r e on Lk Hon 01. We estimate that about seven of our s p e c t r a cover the extent of Knapp's (1976) work. T h e i r s p e c t r a show the same extended v e l o c i t y f e a t u r e s as those of Wilson et a l . (1973). T h i s i r r e g u l a r l y d i s t r i b u t e d s t r u c t u r e d i d not allow a n a l y t i c treatment and nothing f u r t h e r i s s a i d about i t by Knapp et a l . (1976). F i g u r e 1 of Knapp et a l . ( 1 976) shows the Lk HLX101 p r o f i l e as the b r i g h t e s t with a s i g n i f i c a n t temperature drop as one proceeds away from t h i s c e n t r e . The v e l o c i t y of the p r o f i l e s 84 shown i n F i g u r e 2 i s approximately -1 ± 1 km s - 1 . T h i s v e l o c i t y i s r e p r e s e n t a t i v e of a l l of t h e i r p r o f i l e s . S e v e r a l of t h e i r p r o f i l e s show a d i s t i n c t d i p at 0 km s _ 1 . They a t t r i b u t e t h i s d i p to s e l f a b s o r p t i o n . The d i s t r i b u t i o n of the d i p s agrees with that of the dust lanes c r o s s i n g the face of Sh a r p l e s s 222. F i g u r e 18 i s an example of our s p e c t r a showing the d i p . Knapp et a l . (1976) a l s o c l a i m that the s e l f a b s o r p t i o n i s r e s p o n s i b l e f o r the sharp drop i n the 1 2 C 0 r a d i a t i o n temperatures. S e c t i o n IV.2 compares our data to that of Knapp et a l . (1976), n o t i n g the many d i f f e r e n c e s as w e l l as the s i m i l a r i t i e s . 85 F i g u r e 18 - 1 JC0 P r o f i l e Dip This f i g u r e i s r e p r e s e n t a t i v e of the 1 2C0 p r o f i l e s e x h i b i t i n g the prominent d i p i n the s p e c t r a l l i n e . Approximately 30 per cent of our p o s i t i o n s i n d i c a t e d the presence of t h i s d i p . These p o s i t i o n s appeared to be randomly o r i e n t e d and d i d not appear to be r e l a t e d t o dark lanes. Since the d i p s are not w e l l resolved and the s p e c t r a l p o s i t i o n s are randomly d i s t r i b u t e d we could not do a proper v e l o c i t y a n a l y s i s . 86 IV.2-0ur Observations Of the four components o u t l i n e d i n the p r e v i o u s s e c t i o n we have covered the f i r s t two i n d e t a i l . Lk HC*101 appears to be an e a r l y type s t a r , probably BO.5, with a small a s s o c i a t e d HII r e g i o n . From the r a d i o o b s e r v a t i o n s the s i z e of the HII region i s l e s s than one arcsecond. Surrounding the HII region i s a more extended area of f a i n t e r emission of r a d i u s 32 arcseconds. T h i s s e c t i o n covers the d e t a i l s of the two l a r g e r components. They are the HI c l o u d and the molecular c l o u d . F i g u r e 19 shows an enlarged red Palomar p r i n t . P l a s t i c o v e r l a y s of the r e s u l t s of t h i s p r o j e c t and Dewdney and Roger's (1981) HI data are l o c a t e d i n the envelope on the back j a c k e t of the t h e s i s . The c e n t r e of each o v e r l a y i s i n d i c a t e d with a c r o s s . A l l of the o v e r l a y s are drawn to the same s c a l e as the photograph i n F i g u r e 19 and may be p o s i t i o n e d with the a i d of the four guide s t a r s i n d i c a t e d . A f u l l d i s c u s s i o n of the r e s u l t s i s given below. Palomar p r i n t s show an e x c i t i n g s t a r , Lk HCX101, surrounded by the nebula NGC 1579. The c e n t r a l b r i g h t nebula i s approximately f i v e arcminutes a c r o s s . F a i n t e r emission to about s i x arcminutes from the c e n t r e surrounds the nebula. The HII r e g i o n i s embedded i n a very long o b s c u r i n g c l o u d of angular extent three degrees. The average v i s u a l e x t i n c t i o n of t h i s e longated molecular c l o u d i s about two magnitudes. A s t a r count a n a l y s i s i n d i c a t e s small 'pockets' of strong v i s u a l e x t i n c t i o n . The maximum v i s u a l e x t i n c t i o n measured i s at l e a s t f i v e magnitudes. Using the r a t i o of H atoms to v i s u a l e x t i n c t i o n , A v, 87 from B o h l i n et al» (1978) one would i n f e r a mean t o t a l hydrogen column d e n s i t y of 4 x 10 2' atoms cm - 2 with 'pockets' up to 10 x 1 0 2 1 atoms cm" 2. Table VIII at the end of t h i s s e c t i o n l i s t s hv r e s u l t s d e r i v e d from the generated 1 3CO column d e n s i t i e s f o r each of the c l o u d s (Dickman 1978, B o h l i n et a l . 1978). The v i s u a l e x t i n c t i o n from the 1 3CO range from .8 to 15 magnitudes. T h i s i s i n e x c e l l e n t agreement with the value of 11 magnitudes obtained by Dewdney and Roger (1981) but not i n agreement with our c a l c u l a t i o n s of the v i s u a l e x t i n c t i o n from the s t a r counts. The e x t i n c t i o n s from the s t a r count a n a l y s i s are probably too low. Our 1 2CO o b s e r v a t i o n s i n d i c a t e a l i n e v e l o c i t y of -1.25 km s~ 1 with a h a l f width of 2 km s ~ 1 . The p r o f i l e s are sharper and narrower than a gaussian p r o f i l e . Our v e l o c i t y corresponds e x a c t l y with that found by Knapp et a l . (1976) and Wilson et a l . (1973). T h i s i s a l s o t rue f o r the v e l o c i t y h a l f width. In approximately t h i r t y per cent of our p r o f i l e s there i s a d i s t i n c t d i p i n the p r o f i l e c e n t r e at 0 km s" 1 ( F i g u r e 18). Knapp et a l . (1976) note the presence -of t h i s d i p i n two of t h e i r s p e c t r a and on t h i s b a s i s they c l a i m that the d i p i s the r e s u l t of s e l f - a b s o r p t i o n of the 1 2CO emission i n dark lanes that cut a c r o s s the face of S h a r p l e s s 222. We f i n d there i s no c o r r e l a t i o n between the 1 2CO d i p and the presence of dark l a n e s . These p r o f i l e d i p s are d i s t r i b u t e d q u i t e randomly throughout our s p e c t r a l p o s i t i o n s and so a n a l y s i s of the s p e c t r a i n terms of two v e l o c i t y components i s not p o s s i b l e . Dewdney and Roger (1981) found no evidence f o r d i f f e r e n t v e l o c i t y components i n HI and suggest s e l f - a b s o r p t i o n as the cause f o r the p r o f i l e d i p s . 88 Astronomers o f t e n make s i m p l i f y i n g L.T.E. assumptions i n determining e x c i t a t i o n temperatures and column d e n s i t i e s , o f t e n without adequate j u s t i f i c a t i o n . A non l o c a l thermodynamic e q u i l i b r i u m (non L.T.E.) r a d i a t i v e t r a n s f e r program, developed by Hobbs and Shuter (1981) from Bernes' (1979) Monte C a r l o method, shows that the di p s i n the p r o f i l e s are a consequence of the d i f f e r e n t assumed c o n d i t i o n s of non L.T.E. as opposed to L.T.E. Hobbs and Shuter (1981) f i n d pronounced d i p s that decrease from a maximum d i p i n the p r o f i l e at the c l o u d c e n t r e to no d i p at the o u t s k i r t s of the c l o u d . Our v e l o c i t y r e s o l u t i o n i s not f i n e enough to support t h i s c o n c l u s i o n . We do f i n d the d i p s more o f t e n at the c l o u d c e n t r e s but cannot say t h i s i s a consequence on non L.T.E. c o n d i t i o n s s i n c e these d i p s may j u s t be noise on top of the p r o f i l e s . We a l s o f i n d a few p r o f i l e s on the edge of the c l o u d that have d i p s . P r o f i l e d i p s at the c l o u d edge are p r e d i c t e d using models with a more complicated geometry w i t h i n the c l o u d . At present, the program i s s t i l l i n the developmental stage. With b e t t e r v e l o c i t y r e s o l u t i o n and b e t t e r s i g n a l to noise one should be abl e to d i s t i n g u i s h between nois e and r e a l f e a t u r e s such as these d i p s . Our peak r a d i a t i o n temperature was 20 ± 2 K. Our s i g n a l to rms no i s e r a t i o averaged between e i g h t and ten f o r s p e c t r a with an observed s i g n a l . The v e l o c i t y h a l f width decreased s l i g h t l y from 2.5 to 1.5 km s~ 1 towards the edge of the o b s e r v a t i o n f i e l d . The 1 2CO r a d i a t i o n temperature d i s t r i b u t i o n can be d e s c r i b e d as a warm background (10 K) with a fragmented hot 89 c l o u d southeast of Lk HO(101. S e v e r a l regions of c o o l gas (5 K) are l o c a t e d adjacent to the hot c l o u d (Figure 7). When the 1 2C0 v e l o c i t y h a l f width i s combined with the T f t ( 1 2C0) i n a column d e n s i t y c a l c u l a t i o n , the hot and c o l d spots are more c l e a r l y d i s t i n g u i s h e d . T h i s i s i l l u s t r a t e d by the N C O L ( 1 3 C O ) contours ( F i g u r e 10). The generated 1 3CO r a d i a t i o n temperature d i s t r i b u t i o n d e s c r i b e d i n s e c t i o n III.4 (Figure 10) shows the same f e a t u r e s as 1 2CO (Figure 7). Due to the nature of the TA* ( 1 2CO) to T A ( 1 3CO) r a t i o the f e a t u r e s present i n the 1 3CO contour map are c l e a r e r s i n c e the r a t i o emphasizes 1 2CO hot spots. Any fe a t u r e on the 1 3CO map but not present i n 1 2CO i s not r e s o l v e d . The 1 3CO column d e n s i t y , N C 0 1_( 1 3C0), combines the c l a r i t y of T* ( 1 3CO) with the v a r i a t i o n of the h a l f width of 1 2CO, A V ( 1 2 C O ) . The net r e s u l t i s three w e l l r e s o l v e d fragments and p o s s i b l y two others i n s i d e a broad region of c o o l e r molecular m a t e r i a l (Figure 10). There i s a c r u c i a l d i f f e r e n c e between our r e s u l t s and those of Knapp et a l . (1976). They observe a d r a s t i c temperature d e c l i n e away from t h e i r c e n t r e (Lk HCX101). We do not observe t h i s d e c l i n e . Our ob s e r v a t i o n s i n d i c a t e a general background of CO emission with s e v e r a l hot and c o l d clumps. Examination of the 1 2CO and 1 3CO contours r e v e a l s two p e c u l i a r c o l d regions l o c a t e d at Lk HodOl (-5.4,0.0) and Lk HOO01 ( r . 8 , 5 . 4 ) . The l a t t e r i s a wider r e g i o n of reduced emission that i s p a r t i a l l y overlapped by an area of decreased v i s u a l e x t i n c t i o n , A v , northwest of the peak HI. The former, Lk HCV101 (-5.4,0.0), i s a s i n g l e spectrum with no detected 1 2CO. 90 Surrounding s p e c t r a have moderate emission p r e s e n t . At f i r s t , we supected that t h i s might be the r e s u l t of ins t r u m e n t a l problems. However, the r e c e i v e r system appeared to be working w e l l s i n c e three other p r o f i l e s c o l l e c t e d at the same time showed s i g n i f i c a n t 1 2CO s i g n a l . T h e r e f o r e , t h i s p o s i t i o n probably has no 1 2CO pr e s e n t . Two e x p l a n a t i o n s are p o s s i b l e . E i t h e r there i s no 1 2CO emission i n a long c y l i n d r i c a l hole through the e n t i r e c l o u d or a very c o o l foreground c l o u d i s absorbing the emission. The s t a r counts were repeated i n the v i c i n i t y of Lk HCY101 ("5.4,0.0) us i n g a smaller reseau g r i d . There i s s l i g h t evidence of a very s m a l l obscuring c l o u d below the r e s o l u t i o n of our CO ob s e r v a t i o n s and the o r i g i n a l s t a r counts. From both Palomar p r i n t s no s t a r s were recorded around t h i s p o s i t i o n . The i n t e g r a t e d 1 2CO temperature contours do not show the presence of the hole and Dewdney and Roger (1981) do not f i n d any anomaly in t h e i r HI r e s u l t s at Lk HOM01 (-5.4,0.0). Consequently, we have to regard t h i s f e a t u r e as unresol v e d . What i s r e q u i r e d i s a small e r t e l e s c o p e beam width to map the r e g i o n . Both Wilson et a l . (1973) and Knapp et a l . (1976) found v e l o c i t y s t r u c t u r e i n the wings of the c e n t r a l p r o f i l e . We found no evidence f o r t h i s s t r u c t u r e i n our r e s u l t s . Our temperature r e s o l u t i o n probably p r e c l u d e d seeing t h i s s t r u c t u r e . From Knapp et a l . (1976) the peak temperature of the s t r u c t u r e i s very c l o s e to the noise of our s p e c t r a . The s t r u c t u r e i s a l s o on the edge of. the spectrometer range where a q u a d r a t i c b a s e l i n e f i t was made. The T* ( 1 3CO) and AV( 1 3CO) values from Knapp et a l . (1976) support the f i n d i n g s f o r other Sharpless regions by Sewall 91 (1980). Sewall (1980) found the r a t i o T* ( 1 2CO) to T* ( 1 3CO) was g e n e r a l l y about f i v e . The r e s u l t s of Knapp et a l . (1976) f o r t h e i r two sp e c t r a f o r Sharpless 222 co n f i r m t h i s . Furthermore, Sewall (1980) found the 1 3CO p r o f i l e s mimicked the shape of the 1 2CO p r o f i l e s and AV( 1 2CO) was approximately 1.5 times wider than A V ( 1 3 C O ) . T h i s agrees with the r e s u l t s of Knapp et a l . (1976). Why do the 1 3CO p r o f i l e s mimick the 1 2CO p r o f i l e s ? A p o s s i b l e reason i s that the 1 3CO l i n e i s p a r t i a l l y s a t u r a t e d . Sewall (1980) found the o p t i c a l depth f o r the 1 3CO was at l e a s t one i n the case of Sharpless 152. I t must be remembered that t h i s i s a lower l i m i t f o r the 1 3CO o p t i c a l depth. As a r e s u l t , i t c o u l d be n a t u r a l to observe s i m i l a r l i n e shapes f o r 1 2CO and 1 3CO i f they are both s a t u r a t e d t r a n s i t i o n s , although t h i s i s not a necessary p r e r e q u i s i t e f o r the 1 2CO and 1 3CO l i n e s to be s i m i l a r . Another r e l a t e d problem i s the det e r m i n a t i o n of the 1 3CO e x c i t a t i o n temperature. Normally, T G A ( 1 3 C O ) i s taken to be the same as T ^ ( 1 2 C O ) . I f the e x c i t a t i o n temperatures were d i f f e r e n t f o r the two i s o t o p i c s p e c i e s then f o r the c o o l e r regions the two p r o f i l e s would be d r a s t i c a l l y d i f f e r e n t from each other. T h i s i s the case f o r c o l d dark g l o b u l e s . For warmer regions such as we have, the two p r o f i l e s are s i m i l a r s i n c e both l i n e s c o u l d be s a t u r a t e d . The i n f r a r e d photograph from the Steward Observatory (Figure 14) shows there i s very l i t t l e c o i n c i d e n c e between i n f r a r e d s t a r s and CO hot spots. One i n t e r e s t i n g f e a t u r e d i d become apparent. Surrounding our 13 K 1 2CO contour are three sets of i n f r a r e d s t a r s . They are i n f r a r e d s t a r s #2, #3, and the 92 s i x s t a r s surrounding Lk Htv 1 0 1 . T h i s i n t e r e s t i n g c o i n c i d e n c e appears to agree with p r e d i c t i o n s of the ' B l i s t e r ' model ( I s r a e l 1977, Gilmore 1978). In t h i s model OB a s s o c i a t i o n s form j u s t i n s i d e the s u r f a c e s of long molecular c l o u d s . Star formation i s i n i t i a t e d on one s i d e of the g i a n t c l o u d and proceeds i n t o the c l o u d . The CO hot spots would then be the next generation of s t a r formation. S i m i l a r but f a r more q u a n t i t a t i v e r e s u l t s were d e r i v e d using numerical models f o r HII regions i n the Champagne model (Tenorio-Tagel 1979). In Sharpless 222 there are probably three generations of s t a r s . Lk HCV101 i s the i n i t i a t i n g s t a r . Habing and I s r a e l ( 1 979) would c l a s s i f y Lk H«101 as the f o u r t h stage i n t h e i r e v o l u t i o n a r y sequence. The other i n f r a r e d s t a r s are the next g e n e r a t i o n which c o u l d be c l a s s e d as the f i r s t stage of the same sequence. The CO hot spots are the most recent stage that precedes s t a r formation. Dewdney and Roger's (1981) peak HI contours and the s i x i n f r a r e d s t a r s around Lk HCX101 are c o i n c i d e n t . The other i n f r a r e d s t a r s appear to have no r e l a t i o n to the HI data. Comparing the CO and HI g l o b a l f e a t u r e s there i s an a n t i c o r r e l a t i o n between the two. The peak HI contours l i e to the northwest of the CO hot spots. T h i s i n d i c a t e s the two s t u d i e s are mapping d i f f e r e n t r e g i o n s . The HI v e l o c i t y h a l f width i s much l a r g e r than the 1 2CO which c o u l d be e x p l a i n e d by the d i f f e r e n c e between the CO and HI p a r t i c l e masses. The v i s u a l e x t i n c t i o n contours show a reasonable c o r r e l a t i o n between the higher and CO warm r e g i o n s . T h i s i s in agreement with the work of Dickman (1978) and F r e r k i n g et a l . 93 (1981). The peak HI emission occurs i n regions where the v i s u a l e x t i n c t i o n i s lower than average. The e x c i t i n g s t a r has presumably been able to d i s s o c i a t e H a i n t o HI to the northwest where A v i s lower. Dewdney and Roger (1981) have modeled t h i s asymmetry q u i t e w e l l by assuming a steep d i s c o n t i n u i t y of d e n s i t y near Lk Hoc 1 01 to the e a s t . Dewdney and Roger (1981) f i n d the peak column d e n s i t y f o r HI i s 13 x 1 0 2 0 atoms cm - 2 and a t o t a l mass of HI of 85M 0. Both estimates must assume the emission c l o u d i s o p t i c a l l y t h i n . Sewall (1980) found that the o p t i c a l depth was q u i t e high ( X >, 1 ) f o r Sharpless regions and so the assumption by Dewdney and Roger (1981) may not be a good one. Dewdney and Roger (1981) a l s o make a rough estimate f o r the peak 1 3CO column d e n s i t y using the r e s u l t s of Knapp et a l . (1976). They f i n d N C 0 L( 1 3CO) i s 2.8 x 1 0 1 S cm - 2 with a corresponding H a column d e n s i t y of 2.1 x 1 0 2 2 atoms cm - 2 and a v i s u a l e x t i n c t i o n of eleven magnitudes. T h i s value of Av i s w e l l w i t h i n other estimates a l r e a d y c i t e d . Our r e s u l t s suggest peak 1 3CO column d e n s i t i e s e x a c t l y the same as Dewdney and Roger (1981) have found from Knapp et a l . (1976). Using the same a n a l y s i s as used by Dewdney and Roger (1981), the peak HI column d e n s i t y i m p l i e d from our generated 1 3CO data would be 1.4 x 1 0 2 1 atoms cm - 2. T h i s i s p r e c i s e l y that found by Dewdney and Roger (1981). The value of the v i s u a l e x t i n c t i o n i m p l i e d from our 1 3CO r e s u l t s f o r each of the clouds i s between 8 and 15 magnitudes (Table V I I I ) . These v a l u e s of kv are w e l l w i t h i n other estimates (Thompson et a l . 1977, Cohen 1980). 94 F i n a l l y , one can c a l c u l a t e the mass of each of the c l o u d fragments from t h e i r s i z e and the generated 1 3C0 column d e n s i t y . The c l o u d s i z e i s d e f i n e d as the width to h a l f power of our generated 1 3 C 0 r a d i a t i o n temperature, T A ( 1 3 C 0 ) , contours. A mass using the v i r i a l theorem can be computed by assuming the cl o u d fragment i s i n e q u i l i b r i u m , supported by t u r b u l e n c e , or by assuming a f r e e f a l l c o l l a p s e with V°^r. Both g i v e , M £ R A V (EVKttS J ^ 8 l ) where R i s the c l o u d r a d i u s and AV i s the l i n e h a l f width of the 1 3CO p r o f i l e s . Note that the v i r i a l mass i s only a very rough estimate r e q u i r e d f o r s t a b i l i t y of the c l o u d . I t i s probably an upper l i m i t . The generated 1 3 C 0 column d e n s i t y can a l s o be used to estimate the c l o u d mass. Then, where A i s the p r o j e c t e d area, m H i s the atomic hydrogen mass (1.67 x 10 ~ 2 * grams), y U , i s the mean molecular weight ( 2 . 3 3 atomic mass u n i t s ) , X i s the r a t i o of H a to 1 3 C 0 from Dickman 95 (1978), and N i s the 1 3 C 0 column d e n s i t y . If N v a r i e s s i g n i f i c a n t l y over the extent of the c l o u d , A•N should be r e p l a c e d by a sum of the A«N over the c l o u d a r e a . The p r o j e c t e d area, A, i s p o o r l y d e f i n e d and depends on d 2 , where d i s the d i s t a n c e . As a r e s u l t , the u n c e r t a i n t i e s i n the mass are l a r g e . G e n e r a l l y , the masses are underestimated. Tables IX and X give a summary of the clouds and t h e i r masses c a l c u l a t e d by both methods. The masses obtained by the two methods d i f f e r s i g n i f i c a n t l y . The true mass of each c l o u d fragment i s probably a compromise between the two est i m a t e s . The work of F r e r k i n g et a l . (1981) probably g i v e s the best masses f o r these warm clouds s i n c e t h e i r r e s u l t s have c o n s i d e r e d the problem of CO isot o p e f r a c t i o n a t i o n . The 1 3C0 column d e n s i t y , N C O L ( 1 3 C O ) , enables one to c a l c u l a t e the t o t a l molecular column d e n s i t y , N, using the Dickman (1978) r a t i o of to 1 3 C 0 . T h i s i s e a s i l y converted to t o t a l atomic hydrogen d e n s i t y and v i s u a l e x t i n c t i o n . The r e s u l t s are given i n Table V I I I . The v i s u a l e x t i n c t i o n s found from the s t a r counts give r e s u l t s much lower than those from the column d e n s i t i e s . Due to the l a r g e u n c e r t a i n t i e s i n the s t a r counting one should not r e l y too h e a v i l y on those r e s u l t s . The v i s u a l e x t i n c t i o n s determined from the s t a r counts are probably f a r too low whereas those found u s i n g the generated 1 3CO column d e n s i t i e s are l i k e l y upper l i m i t s . We f e e l the tr u e value of the v i s u a l e x t i n c t i o n , A v , i s f a i r l y c l o s e to those given by the 1 3CO a n a l y s i s . One f i n a l c a l c u l a t i o n , was made to determine the maximum r e l a t i v e v e l o c i t y d i f f e r e n c e between clouds i f they were i n 96 K e p l e r i a n o r b i t s about each o t h e r . Clouds #1 and #2 l o c a t e d at Lk HCV101 ( 7 . 2 , - 1 0 . 8 ) and Lk HCV101 ( 0 . 0 , - 1 0 . 8 ) were chosen s i n c e they would give the l a r g e s t r e l a t i v e v e l o c i t y d i f f e r e n c e . They are the most massive and nearest neighbours. From the 1 3CO column d e n s i t y mass, the v e l o c i t y d i f f e r e n c e i s at most 0.35 km s ~ 1 . T h i s i s below the spectrometer v e l o c i t y r e s o l u t i o n . I t i s i n t e r e s t i n g to note that the observed d i f f e r e n c e was 0 . 4 km s ~ 1 . Since the v e l o c i t y d i f f e r e n c e s expected are below our v e l o c i t y r e s o l u t i o n no f u r t h e r c o n c l u s i o n s on t h i s aspect of the clouds are p o s s i b l e . £>7 Table VIII -Peak N C O L( 1 3CO) and R e l a t e d A v For each of the f i v e c l o u d s the peak 1 3 C 0 column d e n s i t y i s giv e n . The t o t a l H a column d e n s i t y and corresponding v i s u a l e x t i n c t i o n are c a l c u l a t e d . The l a s t column g i v e s the measured v i s u a l e x t i n c t i o n from the s t a r counts of the Palomar p r i n t s . N C O L(2H a) was found using Dickman's ( 1978) r a t i o , N c c J H j = (5.0 + 2.5) x 10 5 N C O L ( 1 3 C O ) Then an estimate of the v i s u a l e x t i n c t i o n , A v, was determined u s i n g , <N(H, + H 3 k)/E(B-V)> = 5.8 x 1 0 2 1 atoms cm - 2 mag"1 ( B o h l i n et a l . 1978) and A v = 0.76A 6. F r e r k i n g et a l . (1981) have d e r i v e d a l a r g e r value f o r the H to ' 3CO abundance, namely 1.0 x 10 6. T h i s i s twice the Dickman (1978) r e s u l t and g i v e s column d e n s i t i e s twice as l a r g e as those i n d i c a t e d above. The F r e r k i n g r a t i o (1981) takes i n t o account the carbon monoxide isotope f r a c t i o n a t i o n . 98 Cloud Generated N „ u ( 1 3 C 0 ) (xlO 1. 4 cm 2) N(2H a) ( x l O 2 2 cm-2) A v s t a r counts #l-(7.2,-10.8) 287 2.9 15.5 4.0 #2-(0.0,-10.8) 271 2.7 14.6 1.5 #3-(7.2,-5.4) 205 2.1 11.0 2.4 #4-(3.6,-5.4) 193 1.9 10.4 2.2 #5-(0.0,-1.8) 147 1.5 7.9 2.9 99 Cloud 1 3 C 0 S i z e 3.5 k 3.0 k Mass Mo Densit y ( x l O 5 ) amu/cm3 #l-(7.2,-10.8) #2-(0.0,-10.8) #3-(7.2,-5.4) #4-(3.6,-5.4) #5-(0.0,-1.8) 3000 230 420~A 530 / \ 1760 160 \ 180 J 128 370 1.2 1.9 1.1 2.9 6.7 Note: 1 = 1.67 x 1 0 3 4 cm 2 area f o r the 1 3CO s i z e . Table IX - V i r i a l Cloud Masses Tabl e IX i n d i c a t e s the s i z e of each c l o u d c o n t a i n e d w i t h i n two d i f f e r e n t 1 3CO r a d i a t i o n temperature contours and the cor r e s p o n d i n g v i r i a l mass assuming s p h e r i c a l symmetry. The average d e n s i t y i s given i n the l a s t column of the t a b l e . 100 Cloud N ( 1 3 C 0 ) S i z e Mass Den s i t y (xlO 1 5 cm -M ( x l O 4 ) >15 12.5 10 amu/cm3 #l-(7.2,-10.8) 241^ 4 9 V 1.0 #2-(0.0,-10.8) 186 1 41J 1.2 1730 2490 { 370 440 #3-(7.2,-5.4) 128 \ 1.2 #4-(3.6,-5.4) 59/ 1.8 #5-(0.0,-1.8) 7 19 218 ? 7 25 0.7 Note: 1 = 1.67 x 10- 4 cm 2 area f o r the 3C0) s i z e . Table X -N C O L( 1 3CO) Cloud Masses T h i s t a b l e g i v e s the s i z e of each c l o u d c o n t a i n e d w i t h i n three d i f f e r e n t 1 3CO column d e n s i t y contours and the corresp o n d i n g 1 3CO column d e n s i t y mass. The average d e n s i t y i s given i n the l a s t column of the t a b l e . F r e r k i n g et a l . (1981) have d e r i v e d a l a r g e r value f o r the H a to 1 3CO abundance, namely 1.0 x 10 6. T h i s i s twice the Dickman (1978) r e s u l t and g i v e s column d e n s i t y masses twice as l a r g e as those i n d i c a t e d above. The F r e r k i n g r a t i o takes i n t o account the problem of CO isotope f r a c t i o n a t i o n . Figure 19 - Comparison o f 1 2 C 0 , HI , A v e t c . F igure 19 i s an enlargement o f the red Palomar b r i h t The s c a l e s i z e i s 6.27 m i l l ime t r e s per 1.8 arcminute i n t e r v a l f i g u r e 7 - I n t e g r a t e d "CO Contours The T* ("CO) i s i n t e g r a t e d over a l l v e l o c i t i e s t o give F i g u r e 7. The d e c l i n a t i o n (DEC) verses r i g h t a s c e n s i o n (RA) p l o t shows f i v e CO hot spots l o c a t e d at (7.2,-10.6), (0.0,-10.6), (7.2,-5.4), (3.6,-5.4), and (0.0,-1.6). The c e n t r e (0.0,0.0) i s , cx(1950) • 04H26"34'.0 (Right Ascension) £(1950) * 35*13'00*0 ( D e c l i n a t i o n ) figure 9 -Generated ("CO) Contours The TJ ("CO) contours are generated frorr "CO observations. The contour units are one kelvin steps. The declination (DEC) verses right ascension (RA) plot shows the sane five CO hot spots present in Figure 7 ( T { ("CO) Contours). The centre (0.0,0.0) i s , O((1950) - 04"26n34!0 (Right Ascension) 6 (1950) - 35*13'00*0 (Declination) F i g u r e 10 Generated N C O t("CO) Contours The N M L(**CO) contours are generated froir "CO o b s e r v a t i o n s . The contour u n i t s are 1 i 10* • dr."*. The d e c l i n a t i o n (DEC) versus r i g h t ascension (RA) p l o t shows the same f i v e CO hot spots present i n F i g u r e 7 (T A" (**CO) Conto u r s ) . To determine N t 0, {''CO), the r a t i o ZVC'CO) t o AV(»»CO) was found t o be 1.52 ± 0.04 (see Table I l l - P r o f i l e H a l f Width R a t i o s ) . The c e n t r e (0.0,0.0) i s , o((1950) - 04 - 26',3«!0 (Right Ascension) 6(1950) « 35 e13'00*0 ( D e c l i n a t i o n ) Figure 13 . (Vr 5500 A ) , A v Extinction Contours The magnitudes of ex t i n c t i o n were determined using the standard procedure outlined i n section III.6-Star Counting Theory, Data, and Results. The numbers on each contour map represent the i n t e r v a l of e x t i n c t i o n . For example, a 4 would indicate the ex t i n c t i o n i s between 3 and 4 magnitudes. T h e conversion procedure i s o u t l i n e d i n Dickman 197E.Centxe (0.0,0.0), cx<1950) - 04* 26"34*.0 (Right Ascension) 6 (1950) - 35B13'00.'0 (Declination) 102 €> F i g u r e 14 - I n f r a r e d Diagram F i g u r e 14 i s a schematic r e p r e s e n t a t i o n of the i n f r a r e d p r i n t (B000 t o 9000 A) sent by Dr. E. Craine of the Steward Observatory, O n i v e r s t i y of A r i z o n a , Tuscon, A r i z o n a . The converging arrows i s the c e n t r e of our survey f i e l d , a(1950) - 04W26',34'.0 (Right Ascension) 6(1950) - 35 e13'O0"0 ( D e c l i n a t i o n ) Lk H°Q01 i s i n d i c a t e d by 10 and the other i n f r a r e d s t a r s i n our o b s e r v a t i o n f i e l d are numbered. The d e t a i l s of each are summarized i n Table V l l - I n f r a r e d S t a r P o s i t i o n s . tt>Z f F i g u r e 17 The c o n t o u r s show HI e m i s s i o n i n t e g r a t e d o v e r t h e v e l o c i t y range -6 t o +10 km s - ' . The c o n t o u r s t e p s c o r r e s p o n d t o i n t e r v a l s c m - 2 i n column d e n s i t y . (Dewdney and Roger of 1.5 x 102° 1981). 103 V. CONCLUSIONS In c o n c l u s i o n , Lk HonOl i s a BO.5 s t a r . The r a d i o core of the HII region i s l e s s than one arcsecond across with a more extended r e g i o n of weaker emission out to 32 arcseconds. V i s u a l l y , NGC 1579 i s a f i v e arcminute nebula surrounded by a 24 arcminute s h e l l of weaker emission of l i g h t . Our 1 2CO r e s u l t s show a wide region of 1 2CO emission (10 K), but the exact boundaries are as yet undetermined. The north and west boundaries have been determined. We suspect the emission extends as f a r as a v i s u a l e x t i n c t i o n of one magnitude, which covers an area n e a r l y one degree wide and s e v e r a l degrees in l e n g t h . The average r a d i a t i o n temperature, T* ( 1 2 C O ) , i s 10 K. Within our survey f i e l d we found a l a r g e fragmented region with f i v e hot spots of up to 20 K. Since 1 3CO was not observed 1 3CO data were generated from the 1 2CO o b s e r v a t i o n s . Both the 1 2CO and 1 3CO T^ contours have f i v e hot spots w i t h i n a s i n g l e envelope of CO emission l o c a t e d southeast of Lk H C X 1 0 1 . CO clouds # 1 , Lk H<X101 ( 7 . 2 , - 1 0 . 8 ) , #2, Lk H C X 1 0 1 ( 0 . 0 , - 1 0 . 8 ) , and #3, Lk Hcvi 01 (7.2,"5.4) are r e s o l v e d . T h e i r masses d e r i v e d from c a l c u l a t e d 1 3CO column d e n s i t i e s are 49M G, 4 1 M 0 , and 25M Q r e s p e c t i v e l y . Two other unresolved clouds are l o c a t e d at Lk HC X101 ( 3 . 6 , - 5 . 4 ) and Lk HaiOl ( 0 . 0 , - 1 . 8 ) . They are clouds # 4 and #5 and have masses of 1 1 M @ and 25M S. A l l of the fragments are embedded in the same 13 K 1 2CO contour centered on Lk HcnOl (3.6,-7.2). Comparing the CO data to Dewdney and Roger's (1981) HI data, we f i n d an a n t i c o r r e l a t i o n between the p o s i t i o n s of the peak contours of the two s t u d i e s . The HI contours l i e to the 1 04 northwest of the CO contours. T h i s i n d i c a t e s that these two d i f f e r e n t t r a c e r s are mapping separate r e g i o n s . The HI v e l o c i t y h a l f width i s l a r g e r than that f o r the 1 2CO. The d e r i v e d peak HI column d e n s i t i e s from both t r a c e r s are ^1.3 x TO 2 1 atoms cm" 2. The v i s u a l e x t i n c t i o n contours show a reasonable c o r r e l a t i o n between the higher A v and CO warm r e g i o n s . T h i s i s in agreement with the work of Dickman (1978) and F r e r k i n g et a l . (1981). The peak HI emission occurs i n regions where the v i s u a l e x t i n c t i o n i s lower than average. The e x c i t i n g s t a r has presumably been able to d i s s o c i a t e H a i n t o HI to the northwest where A v i s lower. Dewdney and Roger (1981) have modeled t h i s asymmetry q u i t e w e l l by assuming a steep d i s c o n t i n u i t y of d e n s i t y near Lk HO<101 to the e a s t . Surrounding our 13 K 1 2CO contour are three sets of i n f r a r e d s t a r s . They are i n f r a r e d s t a r s #2, #3, and the s i x surrounding Lk Hod 01 (Table V I I ) . T h i s i n t e r e s t i n g c o n f i g u r a t i o n agrees with the p r e d i c t i o n s of the ' B l i s t e r ' model ( I s r a e l 1977, Gilmore 1978). Star formation was l i k e l y i n i t i a t e d on the o u t s k i r t s of the c l o u d and has proceeded inwards. The CO hot spots we observe would be the next generation of i n f r a r e d s t a r s . C o n f i r m a t i o n w i l l r e q u i r e a more d e t a i l e d mapping with b e t t e r r e s o l u t i o n of the region c e n t e r e d on Lk H#1 0 1 (3.6,-7.2) and 1 3CO o b s e r v a t i o n s throughout the r e g i o n . 105 BIBLIOGRAPHY A l l e n , D.A. 1973, Monthly N o t i c e s Royal A s t r o n . Soc. 161:1P. A l l e n , CW. 1963, A s t r o p h y s i c a l Q u a n t i t i e s , U n i v e r s i t y of London, London, Athalone P r e s s . A l t e n h o f f , W.J., Braes, L.L.E., Olnon, F.M., and Wendker, H.J. 1976, A s t r o n . Astrophys. 46:11. Bernes, C. 1979, A s t r o n . Astrophys. 73:67. B o h l i n , R.C., Savage, B.D., and Drake, J.F. 1978, Ap.J. 224:132. Bok, B.J. 1937, "The D i s t r i b u t i o n of S t a r s i n Space", Chicago, U n i v e r s i t y of Chicago P r e s s . B l i t z , L., and Lada, C.J. 1979, Ap.J. 227:152. Braun, R. 1980, Physics 449 D i r e c t e d S t u d i e s Report, U n i v e r s i t y of B r i t i s h Columbia. Brown, R.L., B r o d e r i c k , J . J . , and Knapp, G.R. 1976, Monthly N o t i c e s Royal A s t r o n . Soc. 175:87P. Bruyn, J.R. de 1979, Physics 449 D i r e c t e d S t u d i e s Report, U n i v e r s i t y of B r i t i s h Columbia. Cohen, M. 1980, Monthly N o t i c e s Royal A s t r o n . Soc. 190:865. Cohen, M., and Dewhirst, D.W. 1970, Nature 228:1077. Cohen, M., and Kuhi, L.V. 1979, Ap.J. Suppl. 41:743. Cohen, M., and Woolf, N.J. 1971, Ap.J. 169:543. C r a i n e , E. 1981, p r i v a t e communication (unpublished d a t a ) . Dewdney, P.C., and Roger, R.S. 1981, p r i v a t e communication (unpublished d a t a ) . Dickman, R.L. 1976, Ph.D. D i s s e r t a t i o n , Columbia U n i v e r s i t y . Dickman, R.L. 1978, Ap.J. Suppl. 37:407. Elmegreen, B.G., and Lada, C.J. 1977, Ap.J. 214:725. Evans I I , N.J. 1981, IAU Symp. #87 page 1, R i e d e l Pub., H o l l a n d . F e l l i , M. , and Churchwell, E. 1972, A s t r o n . Astrophys. Suppl. 5:369. F r e r k i n g , M.A., Langer, W.D., and Wilson, R.W. 1981, p r e p r i n t "The R e l a t i o n s h i p Between Carbon Monoxide Abundance and V i s u a l E x t i n c t i o n i n I n t e r s t e l l a r Clouds." 106 Gilmore, W.S. 1978, Ph.D. D i s s e r t a t i o n , U n i v e r s i t y of Maryland. G o l d r e i c h , P., and Kwan, J . 1974, Ap.J. 189:441. Grasdalen, G.L., and Gaustad, J.E. 1971, A s t r o n . J . 76:231. Habing, H.J., and I s r a e l , F.P. 1979, Annual Review A s t r o n . Astrophys. 17:345. H a r r i s , S. 1976, Monthly N o t i c e s Royal A s t r o n . Soc. 174:601. Herbig, G.H. 1956, Publ. A s t r o n . Soc. P a c i f i c 68:353. Herbig, G.H. 1971, Ap.J. 169:537. Hobbs, P., and Shuter, W.L.H. 1981, p r i v a t e communication. Hubble, E. 1922, Ap.J. 56:162. I s r a e l , F.P. 1977, Ph.D. D i s s e r t a t i o n , U n i v e r s i t y of Leiden. Knapp, G.R., Kuiper, T.B.H., Knapp, S.L., and Brown, R.L. 1976, Ap.J. 206:443. Mahoney, M.J. 1976, Ph.D. D i s s e r t a t i o n , U n i v e r s i t y of B r i t i s h Columbia. Neugebauer, G., and Leight o n , R.B. 1969, Two Micron Sky Survey:A P r e l i m i n a r y Catalogue NASA SP-3047. Osterbrook, D.E. 1974, " A s t r o p h y s i c s of Gaseous Nebulae", San F r a n s i s c o , Freeman. Panagia, N. 1973, A s t r o n . J . 78:929. Pease, F.G. 1917, Ap.J. 46:24. Penzias, A.A., J e f f e r t s , K.B., and Wilson, R.W. 1971, Ap.J. 165:229. Penzias, A.A., Solomon, P.M., and J e f f e r t s , K.B. 1972, Ap.J. 174:L43. R i e g e l , K.W. 1967, Ap.J. 148:87. R h i j n , P.J. van 1929, Groningen Publ. 43. Schwartz, P.R., and Spencer, J.H. 1977, Monthly N o t i c e s Royal A s t r o n . Soc. 180:297. Sewall, J.R. 1980, Second Year Research P r o j e c t , U n i v e r s i t y of Maryland. S h a r p l e s s , S.L. 1959, Ap.J. Suppl. 4:257. 1 07 Shuter, W.L.H., and McCutcheon, W.H. 1974, Royal A s t r o n . Soc. Canada Jour. 68:301. Simon, T., and Dyck, H.M. 1977, A s t r o n . J . 82:725. Spencer, J.H., and Schwartz, P.R. 1974, Ap.J. 188:L105 S t r e c k e r , D.W., and Ney, E.P. 1974, A s t r o n . J . 79:797. Szabo, A. 1980, M.Sc. D i s s e r t a t i o n , U n i v e r s i t y of B r i t i s h Columbia. T e n o r i o - T a g l e , G. 1979, A s t r o n . Astrophys. 71:59. Thompson, R.I., and Reed, M.A. 1976, Ap.J. 205:L159. Thompson, R.I., E r i c k s o n , E.F., Witteborn, F.C., and S t r e c k e r , D.W. 1976, Ap.J. 210:L31. Thompson, R.I., S t r i t t m a t t e r , P.A., E r i c k s o n , E.F., Witteborn, F.C., and S t r e c k e r , D.W. 1977, Ap.J. 218:170. Turner, B.E. 1971, Astrophys. L e t t . 8:73. U l i c h , B.L., and Haas, R.W. 1976, Ap.J. Suppl. 30:247. Wilson, E.W., J e f f e r t s , K.B., and Penzias, A.A. 1970, Ap.J. 143:1*161. Wilson, W.J., Schwartz, P.R., and E p s t e i n , E.E. 1973, Ap.J. 183:871. Zuckerman, B., and Palmer, P. 1974, Annual Review A s t r o n . Astrophys. 12:279. 108 APPENDIX: T / " ( 1 2 C O ) CONTOURS AT CONSTANT VELOCITY In t h i s appendix we present T A ( 1 2CO) contours at constant L.S.R. v e l o c i t y f o r the J=1—»0 t r a n s i t i o n of 1 2CO i n Sha r p l e s s 222. The method of r e d u c t i o n i s d e s c r i b e d f u l l y i n s e c t i o n I I I . 3 . In these f i g u r e s we s p e c i f y the i s o t o p e , the v e l o c i t y and the contour i n t e r v a l (K). The contour u n i t was chosen to represent the average peak to peak nois e f o r the data. 1 0 9 n 12.0 9.333 6.667 _ J I RA. A R C M I N . 4.0 1.333 -1.333 _ l I 1 -4.0 -6.667 -9.333 -]2o0 LH10) 12C0 CONTOUR UNIT -.2.00 K VELOCITY - 3 . 8 5 KM/SEC. 12.0 9.333 6.667 4.0 RR i ~ r 1.333 -] ARCMIN . 333 -4.0 I -6.667 -9.333 -12.0 110 o !2.0 9.333 _J Rfl. ARCMIN. 6 66T 4.0 1.333 -1.333 -4.0 _ j I I I 1 -6.667 -9.333 -J2cO cr LH101 12C0^^ ? CONTOUR UNrr\-.2.00 Kj VELOCITY -3.20 KM/SEC. 7 \ 12.0 9.333 6.661 4.0 1 1 1.333 -1.333-Rfl. ARCMIN. DEC. ARCMIN -14.D — JI .111 -B.222 -5.133 -2.444 0.444 3.3.33 6.222 .9.111 !2.0 I I I I I ' I ' ' ! i s , •14.0 -11.111 -R.222 -5 .333 -2.444 0.444 3.333 6.222 9.1)1 12.€ DEC. ARCMJN 1 12 RA. A R C M I N . . a 12.0 9.333 6.66') 4.0 1.333 -1.333 -4.0 -6.667 -9.333 -12<rf) RA. A R C M I N . 1 1 3 RA. A R C M I N . 114 o 13.0 10.111 7.222 Rf l . A R C M I N . 4.333 1.444 -1.444 -4.333 I 1 — 1 -7.222 -10.11) -13o0 c r LU a LH101 12C0 CONTOUR mnj-2 V E L O C I T Y . ^ T e O K M / S E C 13.0 10.111 7.222 -1 r — 1 1 4 333 1.444 -1.444 -4.333 Rf l . A R C M I N . -i 1 -7.222 -10.111 DC c r o LU o -13.0 1 1 5 1 1 6 a 13.0 10.111 7 .222 I Rf l . A R C M I N . 4.333 1.444 __1 1_ -1 .444 _l -4.333 -7.222 _ J I -10.111 I -13trfl LH101 12C0 CONTOUR UNtT :2 .00 K VELOCITY 0 . 7 0 KM/SEC s: -Qi c r UJ a 13.0 T " 10.111 7.222 —1 1 1 4.333 1.444 -1.444 Rf l . APvCMIN. "T" -4.333 -7.222 -10.111 -13.0 ! i n I 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0085210/manifest

Comment

Related Items