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Durham University

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Publication details for Dr Matteo Fossati

Übler, H., Genzel, R., Wisnioski, E., Schreiber, N. M. Förster, 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. I., Fabricius, M., Galametz, A., Herrera-Camus, R., Lang, P., Lutz, D., Momcheva, I. G., Naab, T., Nelson, E. J., Saglia, R. P., Tadaki, K., Dokkum, P. G. van & Wuyts, S. (2019). The Evolution and Origin of Ionized Gas Velocity Dispersion from z ∼ 2.6 to z ∼ 0.6 with KMOS3D. The Astrophysical Journal 880: 48.

Author(s) from Durham

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 σ0. We find a reduction of the average intrinsic velocity dispersion of disk galaxies as a function of cosmic time, from σ0∼45 km s−1 at z∼2.3 to σ0∼30 km s−1 at z∼0.9. There is substantial intrinsic scatter (ss » 10 km s- ,int 1 0 ) around the best-fit σ0–z relation beyond what can be accounted for from the typical measurement uncertainties (δσ0≈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 ∼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-theart analytical model of galaxy evolution.