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The KMOS Deep Survey (KDS) I : dynamical measurements of typical star-forming galaxies at at z ≃ 3.5.

Turner, O.J. and Cirasuolo, M. and Harrison, C.M. and McLure, R.J. and Dunlop, J.S. and Swinbank, A.M. and Johnson, H.L. and Sobral, D. and Matthee, J. and Sharples, R.M. (2017) 'The KMOS Deep Survey (KDS) I : dynamical measurements of typical star-forming galaxies at at z ≃ 3.5.', Monthly notices of the Royal Astronomical Society., 471 (2). pp. 1280-1320.


We present dynamical measurements from the KMOS (K-band Multi-Object Spectrograph) Deep Survey (KDS), which is comprised of 77 typical star-forming galaxies at z z ≃ 3.5 in the mass range 9.0 < log(M⋆/M⊙) < 10.5. These measurements constrain the internal dynamics, the intrinsic velocity dispersions (σint) and rotation velocities (VC) of galaxies in the high-redshift Universe. The mean velocity dispersion of the galaxies in our sample is σint=70.8+3.3−3.1kms−1 σint=70.8−3.1+3.3kms−1 , revealing that the increasing average σint with increasing redshift, reported for z ≲ 2, continues out to z ≃ 3.5. Only 36 ± 8% of our galaxies are rotation-dominated (VC/σint > 1), with the sample average VC/σint value much smaller than at lower redshift. After carefully selecting comparable star-forming samples at multiple epochs, we find that the rotation-dominated fraction evolves with redshift with a z−0.2 dependence. The rotation-dominated KDS galaxies show no clear offset from the local rotation velocity-stellar mass (i.e. VC − M⋆) relation, although a smaller fraction of the galaxies are on the relation due to the increase in the dispersion-dominated fraction. These observations are consistent with a simple equilibrium model picture, in which random motions are boosted in high-redshift galaxies by a combination of the increasing gas fractions, accretion efficiency, specific star-formation rate and stellar feedback and which may provide significant pressure support against gravity on the galactic disk scale.

Item Type:Article
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:31 May 2017
Date deposited:07 June 2017
Date of first online publication:03 June 2017
Date first made open access:No date available

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