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arXiv · 1906.02737

The Evolution and Origin of Ionized Gas Velocity Dispersion from $z\sim2.6$ to $z\sim0.6$ with KMOS$^{\rm 3D}$

Hannah D. N. Übler·Reinhard Genzel·Emily Wisnioski·Natascha M. Förster Schreiber·T. Taro Shimizu·Sedona H. Price·Linda J. Tacconi·Sirio Belli·David J. Wilman·Matteo Fossati·J. Trevor Mendel·Rebecca L. Davies·Alessandra Beifiori·Ralf Bender·Gabriel B. Brammer·Andreas Burkert·Jeffrey Chan·Richard I. Davies·Maximilian Fabricius·Audrey Galametz·Rodrigo Herrera-Camus·Philipp Lang·Dieter Lutz·Ivelina G. Momcheva·Thorsten Naab·Erica J. Nelson·Roberto P. Saglia·Ken-ichi Tadaki·Pieter G. van Dokkum·Stijn Wuyts
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Abstract

We present the $0.6<z<2.6$ evolution of the ionized gas velocity dispersion in 175 star-forming disk galaxies based on data from the full KMOS$^{\rm 3D}$ integral field spectroscopic survey. In a forward-modelling Bayesian framework including instrumental effects and beam-smearing, we fit simultaneously the observed galaxy velocity and velocity dispersion along the kinematic major axis to derive the intrinsic velocity dispersion $σ_0$. We find a reduction of the average intrinsic velocity dispersion of disk galaxies as a function of cosmic time, from $σ_0\sim45$ km s$^{-1}$ at $z\sim2.3$ to $σ_0\sim30$ km s$^{-1}$ at $z\sim0.9$. There is substantial intrinsic scatter ($σ_{σ_0, {\rm int}}\approx10$ km s$^{-1}$) around the best-fit $σ_0-z$-relation beyond what can be accounted for from the typical measurement uncertainties ($δσ_0\approx12$ km s$^{-1}$), independent of other identifiable galaxy parameters. This potentially suggests a dynamic mechanism such as minor mergers or variation in accretion being responsible for the scatter. Putting our data into the broader literature context, we find that ionized and atomic+molecular velocity dispersions evolve similarly with redshift, with the ionized gas dispersion being $\sim10-15$ km s$^{-1}$ higher on average. We investigate the physical driver of the on average elevated velocity dispersions at higher redshift, and find that our galaxies are at most marginally Toomre-stable, suggesting that their turbulent velocities are powered by gravitational instabilities, while stellar feedback as a driver alone is insufficient. This picture is supported through comparison with a state-of-the-art analytical model of galaxy evolution.

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Hannah D. N. Übler, Reinhard Genzel, Emily Wisnioski, Natascha M. Förster Schreiber, T. Taro Shimizu, Sedona H. Price, Linda J. Tacconi, Sirio Belli, David J. Wilman, Matteo Fossati, J. Trevor Mendel, Rebecca L. Davies, Alessandra Beifiori, Ralf Bender, Gabriel B. Brammer, Andreas Burkert, Jeffrey Chan, Richard I. Davies, Maximilian Fabricius, Audrey Galametz, Rodrigo Herrera-Camus, Philipp Lang, Dieter Lutz, Ivelina G. Momcheva, Thorsten Naab, Erica J. Nelson, Roberto P. Saglia, Ken-ichi Tadaki, Pieter G. van Dokkum, Stijn Wuyts. 2019-06-06. The Evolution and Origin of Ionized Gas Velocity Dispersion from $z\sim2.6$ to $z\sim0.6$ with KMOS$^{\rm 3D}$. https://doi.org/10.3847/1538-4357%2Fab27cc

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