The KMOS Redshift One Spectroscopic Survey (KROSS): the origin of disc turbulence in z approximate to 1 star-forming galaxies

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Johnson, H. L., Harrison, C. M., Swinbank, A. M., Tiley, A. L., Stott, J. P., Bower, R. G., Smail, Ian, Bunker, A. J., Sobral, D., Turner, O. J., Best, P., Bureau, M., Cirasuolo, M., Jarvis, M. J., Magdis, G., Sharples, R. M., Bland-Hawthorn, J., Catinella, B., Cortese, L., Croom, S. M., Federrath, C., Glazebrook, K., Sweet, S. M., Bryant, J. J., Goodwin, M., Konstantopoulos, I. S., Lawrence, J. S., Medling, A. M., Owers, M. S., Richards, S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2018
• Subjects: Galaxies: evolution; Galaxies: high-redshift; Galaxies: kinematics and dynamics; Infrared: galaxies; Kross; sami
• Online Access: https://espace.library.uq.edu.au/view/UQ:d4f0a34/UQd4f0a34_OA.pdf; https://espace.library.uq.edu.au/view/UQ:d4f0a34

We analyse the velocity dispersion properties of 472 z similar to 0.9 star-forming galaxies observed as part of the KMOS Redshift One Spectroscopic Survey (KROSS). The majority of this sample is rotationally dominated (83 +/- 5 per cent with v(C)/sigma(0) > 1) but also dynamically hot and highly turbulent. After correcting for beam smearing effects, the median intrinsic velocity dispersion for the final sample is sigma(0) = 43.2 +/- 0.8 kms(-1) with a rotational velocity to dispersion ratio of v(C)/sigma(0) = 2.6 +/- 0.1. To explore the relationship between velocity dispersion, stellar mass, star formation rate, and redshift, we combine KROSS with data from the SAMI survey (z similar to 0.05) and an intermediate redshift MUSE sample (z similar to 0.5). Whilst there is, at most, a weak trend between velocity dispersion and stellar mass, at fixed mass there is a strong increase with redshift. At all redshifts, galaxies appear to follow the same weak trend of increasing velocity dispersion with star formation rate. Our results are consistent with an evolution of galaxy dynamics driven by discs that are more gas rich, and increasingly gravitationally unstable, as a function of increasing redshift. Finally, we test two analytic models that predict turbulence is driven by either gravitational instabilities or stellar feedback. Both provide an adequate description of the data, and further observations are required to rule out either model.