Surveys of Ultraluminous Activity in the Distant Universe

Abstract

In the last twenty years sub-millimetre surveys have uncovered numerous sub-millimetre bright galaxies (SMGs), sites of some of the most intense star-formation in history with rates peaking over a thousand solar masses per year. For the majority of the twenty years since their discovery, the identification and the constraints on the properties of individual SMGs has been limited by the relatively coarse resolution of single-dish sub-millimetre telescopes (typically FWHM ). The more recent development of millimetre interferometers, such as the Atacama Large Millimetre/Sub-millimetre Array (ALMA), provides us with an order of magnitude increase in resolution over the single-dish surveys allowing us to precisely identify the individual SMGs. In this thesis I present an analysis of two surveys of single-dish sub-millimetre sources which have been followed up with ALMA to identify the individual SMGs. The first survey is of the 716 SCUBA-2 sources detected in the UKIDSS UDS field where our ALMA follow-up detects 708 SMGs. From the extensive multi-wavelength coverage in this field we derive photometric redshifts for each SMG, finding a median with a high-redshift tail containing 33 of SMGs. We find the blending of multiple galaxies into a single-dish source in of our ALMA maps, and this rate of multiplicity increasing for brighter single-dish flux with a rate of 282 for mJy. The photometric redshifts of these multiples suggest 30 are physically associated, which potentially points to merger activity playing a role in the intense star-formation rates for a significant percentage of SMGs. I also present the results of an ALMA survey of four SCUBA-2 sources in the centre of the cluster XCSJ2215, where the high-resolution imaging shows an elevated density of SMGs with 14 detections. Detections of CO in six of these cluster galaxies suggest they are recent accretors with larger fractions of warmer gas than comparable field galaxies suggesting ram pressure stripping is preferentially removing the cold gas content.