Ionized and molecular gas kinematics in a z=1.4 star-forming galaxy

TL;DR

This study combines molecular and ionized gas kinematics in a z=1.4 galaxy to determine its mass distribution, revealing a low dark matter fraction within the effective radius and supporting baryon dominance in such galaxies.

Contribution

It provides a joint analysis of molecular and ionized gas kinematics at high redshift, offering new insights into the mass composition of star-forming galaxies.

Findings

Dark matter fraction within R_e is approximately 0.18.

Molecular and ionized gas kinematics agree well, indicating they trace the same gravitational potential.

Results support baryon dominance in massive z~1-3 star-forming galaxies.

Abstract

We present deep observations of a $z=1.4$ massive, star-forming galaxy in molecular and ionized gas at comparable spatial resolution (CO 3-2, NOEMA; H$\alpha$, LBT). The kinematic tracers agree well, indicating that both gas phases are subject to the same gravitational potential and physical processes affecting the gas dynamics. We combine the one-dimensional velocity and velocity dispersion profiles in CO and H$\alpha$ to forward-model the galaxy in a Bayesian framework, combining a thick exponential disk, a bulge, and a dark matter halo. We determine the dynamical support due to baryons and dark matter, and find a dark matter fraction within one effective radius of $f_{\rm DM}(\leq$$R_{e})=0.18^{+0.06}_{-0.04}$. Our result strengthens the evidence for strong baryon-dominance on galactic scales of massive $z\sim1-3$ star-forming galaxies recently found based on ionized gas kinematics alone.