A kinematic view of galaxy evolution from cosmic noon to today

Chao-Ling Hung

The recent advent of optical/near-infrared and millimeter spectrographs have revealed the internal dynamics of hundreds of star-forming galaxies at 1 < z < 3. At cosmic noon, galaxies located on the star-forming galaxy main sequence (MS) exhibit systematically larger intrinsic velocity dispersions than their local MS counterparts. However, it remains a topic of intense debate as to whether this enhancement in the velocity dispersion is driven by feedback, elevated gas supply, or galaxy interaction. We investigate the origin of this kinematic evolution using a suite of cosmological simulations from the FIRE project. The intrinsic velocity dispersion of galaxies is positively correlated with several quantities such as star formation rate and gas fraction, and these trends are consistent with observations. However, these correlations do not necessarily prove causation. In fact, our simulations suggest that the disturbed kinematics of z~1-2 galaxies are often a result of enhanced gas inflow rates and galaxy interactions. Although gas inflow rates can only be drawn from limited observations currently, future large surveys with Prime Focus Spectrograph will provide the best opportunity to directly probe the interplay between galaxy kinematics, gas inflow, and feedback.