Abstract
Dusty star forming galaxies (DSFGs) are a class of galaxy that are highly dust obscured and are undergoing a period of intense star formation. While a clear picture of these systems at low redshift has emerged, the physical drivers of their star formation and the properties of their interstellar media at high redshift are uncertain. In this thesis I address fundamental questions about these systems such as, what drives their star formation rates, what is the distribution of matter within these galaxies, and how do key properties of their interstellar media, such as their dust temperatures, evolve with redshift.
First, I report on my investigation into whether the star formation rates of three dusty star forming galaxies (ULIRGs) at z ~ 1.5 have merger-driven star formation or if they are driven by secular processes. I analyze their H-alpha rotation curves, rest-frame UV and optical morphologies, and their locations in Gini-M20 space to look for evidence of ordered rotation or ongoing galaxy mergers or interactions. I find that two galaxies are undergoing mergers or interactions and one is an isolated disk, suggesting that unlike at low redshift, ULIRGs at z ~ 1.5 are not all undergoing mergers or interactions.
Next, I report on the serendipitous discovery of a flat outer rotation curve one of the ULIRGs from the previous work -- an isolated disk galaxy at z = 1.6. Flat outer rotation curves are a hallmark of dark matter in galaxies. They are ubiquitous at low redshift but recent studies have reported that galaxies at z > 1 may have declining rotation curves caused by low dark matter fractions and high velocity dispersion support. The rotation curve, ALMA observations of dust continuum emission, and H-band imaging reveal that the dark matter fraction at the H-band half light radius is 0.44+-0.08, which is similar to that of the Milky Way and contrasts with recent works that report dark matter fractions between 0 and 0.2 at the half light radii of star forming galaxies at z > 1. This is one of the first examples in the literature of a flat rotation curve at z > 1.
Finally, I explore whether there is any observational evidence of redshift evolution in the dust temperatures of luminous infrared galaxies between 0 < z < 2. Drawing on three samples containing ~4700 galaxies from the literature that have observations constraining the full wavelength range of the dust SED, I find that the peak wavelength of dust emission (an observational proxy for the luminosity-weighted dust temperature) does not evolve with redshift at fixed IR luminosity. This is in contrast with previous works in the literature that find either that dust temperatures are higher at high redshift than in the local universe, or conversely, that dust temperatures are cooler at high redshift than in the local universe. These contradictory claims arise from the use of a number of different methods for fitting dust SEDs as well as the use of data that does not fully constrain the dust SEDs. Our result highlights the importance of accounting for telescope selection effects both while building a galaxy sample and while fitting the relation between the peak wavelengths of dust emission and the IR luminosities of galaxies.
