UBC Theses and Dissertations
The kinematics of gas and stars in the solar neighbourhood Goulet, Thomas
The kinematic properties of gas and stars in the solar neighbourhood are described in terms of the line-of-sight component of a three-dimensional first order Taylor series expansion of the local velocity field. The types of object analysed are: 1) 21-cm absorbing clouds, 2) HI intercloud medium, 3) main sequence B stars, 4) B stars of luminosity class ranging from I to IV, 5) main sequence A stars, 6) K-giant stars. The least squares fitting procedure used to derive the 10 coefficients describing the fields for various types of objects was essentially the same so that a valid comparison could be made. Marked departures from circular motion are found in most cases but the only systematic trend is a correlation between δu/δx (u being the velocity component along the x-axis directed towards the galactic center) and stellar spectral type, where the gas behaves like a medium "younger" than the early type stars. The analysis of the gas indicates that the standard plane-parallel model provides a good description of the intercloud medium but is inadequate for the absorbing clouds. A velocity ellipsoid description of the residuals is presented for each group of objects. The influence of the Gould belt and of nearby spiral arms on local kinematics is discussed.
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