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Title: The nature and evolution of high redshift dusty star forming galaxies
Author: Greenslade, Joshua
ISNI:       0000 0004 7658 652X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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DSFGs dominate the cosmic star formation rate (SFR) at z > 0.7, are 2 - 3 orders of magnitude more populous at z = 2 than locally, and have SFRs of tens to thousands of solar masses per year. Despite their prodigious SFR, they are heavily dust obscured, with estimates suggesting that optical/UV surveys alone miss half the star formation in the Universe. Furthermore, DSFGs are believed to be the evolutionary progenitors to the massive elliptical galaxies that today inhabit the cores of massive galaxy clusters. DSFGs however remain poorly constrained, with few constraints on their contribution to the cosmic SFR density above z > 4, disagreement over whether single-dish observations accurately reflect the underlying population, and uncertainty about DSFGs in clusters, particularly whether they trace massive overdensities at their epoch. This thesis presents a series of results that set out to address some of these questions. To begin with, and by cross-matching Planck and Herschel data, we identify 27 candidate protoclusters by searching for overdensities of DSFGs. Their colours indicate they likely lie at z = 2 − 3, their flux density is 3x brighter than predicted from models, and fitting modified blackbodies to their photometry suggests they have total SFRs of several thousand solar masses per year. We additionally present the results of an interferometric program targeting 36 single-dish DSFGs at z ∼ 4. We assess their multiplicity, finding that whilst ∼ 45% are blends of multiple sources, there are a number of highly luminous, possibly lensed, singular sources. Finally, we present the serendipitous detection of a SPIRE dropout, a source detected at 850 μm but not at any shorter wavelength, likely at z > 6, and we discuss the application of its selection to wider surveys. In closing, we discuss the future of FIR/sub-mm astronomy, new directions of the work begun here, and the challenges that remain for the field.
Supervisor: Clements, Dave Sponsor: STFC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral