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The KMOS Redshift One Spectroscopic Survey (KROSS) : dynamical properties, gas and dark matter fractions of typical z~1 star-forming galaxies.

Stott, J.P. and Swinbank, A.M. and Johnson, H.L. and Tiley, A. and Magdis, G. and Bower, R. and Bunker, A.J. and Bureau, M. and Harrison, C.M. and Jarvis, M.J. and Sharples, R. and Smail, I. and Sobral, D. and Best, P. and Cirasuolo, M. (2016) 'The KMOS Redshift One Spectroscopic Survey (KROSS) : dynamical properties, gas and dark matter fractions of typical z~1 star-forming galaxies.', Monthly notices of the Royal Astronomical Society., 457 (2). pp. 1888-1904.


The KMOS Redshift One Spectroscopic Survey (KROSS) is an ESO-guaranteed time survey of 795 typical star-forming galaxies in the redshift range z = 0.8–1.0 with the KMOS instrument on the Very Large Telescope. In this paper, we present resolved kinematics and star formation rates for 584 z ∼ 1 galaxies. This constitutes the largest near-infrared Integral Field Unit survey of galaxies at z ∼ 1 to date. We demonstrate the success of our selection criteria with 90 per cent of our targets found to be H α emitters, of which 81 per cent are spatially resolved. The fraction of the resolved KROSS sample with dynamics dominated by ordered rotation is found to be 83 ± 5 per cent. However, when compared with local samples these are turbulent discs with high gas to baryonic mass fractions, ∼35 per cent, and the majority are consistent with being marginally unstable (Toomre Q ∼ 1). There is no strong correlation between galaxy averaged velocity dispersion and the total star formation rate, suggesting that feedback from star formation is not the origin of the elevated turbulence. We postulate that it is the ubiquity of high (likely molecular) gas fractions and the associated gravitational instabilities that drive the elevated star formation rates in these typical z ∼ 1 galaxies, leading to the 10-fold enhanced star formation rate density. Finally, by comparing the gas masses obtained from inverting the star formation law with the dynamical and stellar masses, we infer an average dark matter to total mass fraction within 2.2re (9.5 kpc) of 65 ± 12 per cent, in agreement with the results from hydrodynamic simulations of galaxy formation.

Item Type:Article
Keywords:Galaxies: evolution, Galaxies: kinematics and dynamics, Galaxies: star formation.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:13 January 2016
Date deposited:09 February 2016
Date of first online publication:04 February 2016
Date first made open access:No date available

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