Characterising ultraluminous infrared galaxies in the early universe

• Main Author: Casey, C. M.
• Published: University of Cambridge 2010
• Subjects: 520
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597348

This thesis aims to reduce the effect of selection bias on the understanding of high-<i>z</i> ULIRGs by characterising a population of submillimetre-faint star forming radio galaxies (SFRGs). SFRGs have similarly high star formation rates as SMGs, but I present evidence in this thesis that SFRGs are overall less bolometrically luminous, contain a slightly higher fraction of emission from Active Galactic Nuclei (AGN), and that there is a lack of hotter-dust (&gt;60 K) SFRGs at the highest bolometric luminosities (&gt;10¹³L⊙). In Chapter 2 I present a population of SFRGs which are 70<i>μ</i>m-luminous, showing that they are star formation dominated and have hotter dust temperatures than SMGs of similar luminosities and redshifts. Chapter 3 presents high-resolution MERLIN radio imaging of two <i>z</i> ~ 2 SFRGs who were originally thought to be star formation dominated, but the MERLIN radio imaging combined with a multiwavelength study shows that the systems are actually evolved, low-luminosity AGN. This highlights the usefulness of MERLIN radio observations in breaking degeneracies and characterising galaxies. Chapter 4 presents neutral carbon observations of a set of <i>z</i> ~ 4 SMGs; neutral carbon provides an independent measurement of a galaxy’s star-forming gas reservoir. This serves as a pilot study for future Atacama Large Millimeter Array (ALMA) observations of large samples of high-<i>z</i> ULIRGs.