Study of CO Emission in Nine Hot Dust-Obscured Galaxies at z ∼3

Abstract: Massive galaxies evolve through different phases including starburst-dominated and active galactic nuclei (AGN)-dominated phases. These phases are predicted to be prevalent at earlier times (z ∼ 2 − 3). In this thesis I present high-sensitivity observations from the Atacama Large Millimeter/submillimeter Array to investigate mid-J (Jupper = 4 and 5) CO emission in nine Wide-field Infrared Survey Explorer-selected hyperluminous, hot dust-obscured galaxies (Hot DOGs). These sources are thought to represent a transition phase between starburst- and AGN-dominated galaxies at z ≈ 2.5 − 5. All nine sources are detected in continuum and line emission. I conclude that the sources are gas-rich with Mgas ≈ 1010−11 M . Previous far-infrared spectral energy distribution decomposition revealed that six of the sources have significant cold dust components suggesting high star-formation rates (SFR ≈ 2000 − 9000 M  yr−1 ). The molecular gas in the sources is shown to follow roughly the same star-formation trend as a smaller sample of Hot DOGs and other populations of star-forming and quasar-host galaxies at low- and high-redshift. The resolved CO emission line data displays large velocity dispersions (FWHM ≈ 400 − 900 km s−1 ) consistent with other high-z star-forming and quasar-host galaxies. For a subset of the sources, the line data shows disturbed morphologies and velocity gradients possibly consistent with rotation or galaxy interaction. The results from this analysis suggest that the studied sources are heavily dust-obscured quasars undergoing extreme starburst episodes. The estimated gas and dynamical masses of the sources are consistent with other populations of massive galaxies at low- and high-z, indicating that they likely represent a stage in the evolution of massive galaxies.