The Evolution and Origin of Ionized Gas Velocity Dispersion from z similar to 2.6 to z similar to 0.6 with KMOS3D

Uebler, H.; Genzel, R.; Wisnioski, E.; Schreiber, N. M. Foerster; Shimizu, T. T.; Price, S. H.; Tacconi, L. J.; Belli, S.; Wilman, D. J.; Fossati, M.; Mendel, J. T.; Davies, R. L.; Beifiori, A.; Bender, R.; Brammer, G. B.; Burkert, A.; Chan, J.; Davies, R.; Fabricius, M.; Galametz, A.; Herrera-Camus, R.; Lang, P.; Lutz, D.; Momcheva, I. G.; Naab, T.; Nelson, E. J.; Saglia, R. P.; Tadaki, K.; van Dokkum, P. G. und Wuyts, S. (2019): The Evolution and Origin of Ionized Gas Velocity Dispersion from z similar to 2.6 to z similar to 0.6 with KMOS3D. In: Astrophysical Journal, Bd. 880, Nr. 1, 48

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 KMOS3D integral field spectroscopic survey. In a forward-modeling 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 sigma(0). We find a reduction of the average intrinsic velocity dispersion of disk galaxies as a function of cosmic time, from sigma(0) similar to 45 km s(-1) at z similar to 2.3 to sigma(0) similar to 30 km s(-1) at z similar to 0.9. There is substantial intrinsic scatter (sigma(sigma 0,int) approximate to 10 km s(-1)), around the best-fit sigma(0)-z relation beyond what can be accounted for from the typical measurement uncertainties (delta sigma(0) approximate to 12 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 similar to 10-15 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.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 0004-637X
• Sprache: Englisch