Resolving the properties of massive, high–redshift starbursts

Abstract

Sub-millimeter galaxies (SMGs) are a population of dusty, obscured sources that represent some of the most extreme sites of star-formation in the Universe. These galaxies have total far–infrared (FIR) luminosities of 10E12–10E13Lsol and colossal star formation rates (SFRs) of ∼100–1000 Msol/yr, with the FIR–emission arising due to the reprocessing of ultraviolet radiation from massive, young stars by dust. Despite their discovery nearly 20 years ago, our understanding of the SMG population has been hampered by the coarse resolution (FWHM = 15–30′′) of single-dish sub-millimeter surveys. In this thesis I present observations of FIR–bright (S870>∼1mJy) galaxies that have precise identifications from high-resolution imaging taken with sub–mm/mm interferometers. I present a multi-wavelength study of 96 SMGs that have unambiguous identifications from observations with Atacama Large Millimeter sub–millimeter Array (ALMA) and determine that the photometric redshift distribution for the SMG population has a median of zphot=2.5±0.2. I show that if the star formation activity in SMGs has a timescale of ~100Myr then their descendants at z~0 would have a space density and absolute H –band magnitude distribution that are in good agreement with a volume limited sample of local ellipticals. The low resolution of single-dish surveys has led to concerns about the blending of multiple individual galaxies into a single sub–millimeter source. I present ALMA observations of a sample of 30 bright, single–dish–identified sub-mm sources and show that 61(+19 -15)% are comprised of a blend of multiple SMGs brighter than >∼1mJy. Furthermore, I show that source blending boosts the apparent single-dish number counts by 20% at S870>7.5 mJy. A morphological analysis of the far-infrared emission from a subset of 23 of the brightest sources detected in the ALMA maps shows that the intense starburst in SMGs occurs in a compact region with a median physical half–light diameter of 2.4±0.2kpc. Finally, I present observations of two far–infrared–bright quasars, a potential transition stage in the evolution of SMGs. By considering the gas and black hole properties of these sources I show that they are consistent with the evolutionary scenario where far-infrared bright quasars represent a short phase in the transformation of a starburst dominated SMGs into an unobscured quasar.