UBC Theses and Dissertations
New methods for deblending spectral energy distributions in confused imaging MacKenzie, Todd
The submillimetre band is ideal for studying high-redshift star-forming galaxies, but such studies are hampered by the poor resolution of single-dish telescopes. Interferometric follow-up has shown that many sources are in fact comprised of multiple sources. For many such targets, confusion-limited Herschel observations that target the peak of their far-infrared emission are also available. Many methods for analysing these data have been developed, but most follow the traditional approach of extracting fluxes before model spectral energy distributions are fit, which erases degeneracies among fitting parameters and glosses over the intricacies of confusion noise. We have developed a forward-modelling method in order to tackle this problem in a more statistically rigorous way, which combines source deblending and spectral energy distribution fitting into the same procedure. We adapt our method to three independent projects, all of which benefit from our improved methodology. We investigate a "giant submillimetre arc" behind a massive foreground cluster and uncover seven multiply imaged galaxies, of which six are found to be at a redshift of z~2.9, and possibly constitute an interacting galaxy group. Using our new method, we disentangle the arc into its contributing components and constrain their far-IR properties. Using confusion limited Herschel-SPIRE imaging, the far-IR properties LABOCA detected submillimetre sources can be constrained. Despite such sources often breaking up in high-resolution ALMA imaging, existing studies have implemented traditional fitting methods. We apply our new forward modelling method to re-derive constraints on the far-infrared properties of these sources, exploring selection effects on this sample, while highlighting the benefits of our fitting approach. Finally, we present SCUBA-2 follow-up of 51 candidate proto-cluster fields undergoing enhanced star-formation. With the accompanying Herschel-SPIRE observations and a realistic dust temperature prior, we provide photometric redshift and far-IR luminosity estimates for 172 SCUBA-2 selected sources within the Planck overdensity fields. We find a redshift distribution similar to sources found in cosmological surveys, although our fields are enhanced in both density of sources and star formation rate density over a wide range of redshifts.
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