Speaker
Description
Studies of gas kinematics at z<4 have built a picture where star-forming galaxies evolve from thick gas rich disks at cosmic noon to dynamically cold disks in the local Universe. Pushing these analyses to higher redshifts is crucial for both understanding the origin of the dynamical populations we see in the local universe and tracing their evolution in cosmic time to uncover the conditions for the formation of the first disks.
I will present the first statistical sample of ionised gas kinematics at z>4, focusing on ~250 Ha emitters from the FRESCO and CONGRESS surveys. Kinematic properties such as rotational support, intrinsic velocity dispersion, and dynamical mass, are inferred from the NIRCam grism data using a novel tool GEKO combined with imaging from the JADES survey. By comparing to measurements out to cosmic noon, this analysis places additional constraints on the redshift evolution of the velocity dispersion and rotational support, shedding light on the dynamical properties of early galaxies. These measurements provide crucial insights on the physics of galaxy evolution, especially in light of recent observations of dynamically cold disks at high-redshift and the seeming disagreement with many theoretical models. I will discuss relations between kinematics and star formation and highlight factors driving the increased turbulence we observe. The inferred dynamical masses can be used to obtain constraints on the gas and dark matter fractions in these early systems, providing some of the first benchmark values against which to test predictions from cosmological simulations.
