Final PhD Oral Examination (Thesis Title: “New Methods for Deblending Spectral Energy Distributions in Confused Imaging”)

Speaker: 
TODD MACKENZIE
Event Date and Time: 
Thu, 2015-11-26 12:30 - 14:30
Location: 
Room 200, Graduate Student Centre
Intended Audience: 
Public

ABSTRACT:
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 submm 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-IR 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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