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From peculiar morphologies to Hubble–type spirals : the relation between galaxy dynamics and morphology in star–forming galaxies at z ∼ 1.5.

Gillman, S. and Tiley, A.L. and Swinbank, A.M. and Harrison, C.M. and Smail, I. and Dudzeviciute, U. and Sharples, R.M. and Cortese, L. and Obreschkow, D. and Bower, R.G. and Theuns, T. and Cirasuolo, M. and Fisher, D.B. and Glazebrook, K. and Ibar, E. and Mendel, J. T. and Sweet, S.M. (2020) 'From peculiar morphologies to Hubble–type spirals : the relation between galaxy dynamics and morphology in star–forming galaxies at z ∼ 1.5.', Monthly notices of the Royal Astronomical Society., 492 (1). pp. 1492-1512.


We present an analysis of the gas dynamics of star–forming galaxies at z ∼ 1.5 using data from the KMOS Galaxy Evolution Survey (KGES). We quantify the morphology of the galaxies using HSTCANDELS imaging parametrically and non-parametrically. We combine the Hα dynamics from KMOS with the high–resolution imaging to derive the relation between stellar mass (M*) and stellar specific angular momentum (j*). We show that high–redshift star–forming galaxies at z ∼ 1.5 follow a power-law trend in specific stellar angular momentum with stellar mass similar to that of local late–type galaxies of the form j* ∝ M0.53±0.10∗⁠. The highest specific angular momentum galaxies are mostly disc–like, although generally, both peculiar morphologies and disc-like systems are found across the sequence of specific angular momentum at a fixed stellar mass. We explore the scatter within the j* – M* plane and its correlation with both the integrated dynamical properties of a galaxy (e.g. velocity dispersion, Toomre Qg, Hα star formation rate surface density ΣSFR) and its parameterised rest-frame UV / optical morphology (e.g. Sérsic index, bulge to total ratio, Clumpiness, Asymmetry and Concentration). We establish that the position in the j* – M* plane is strongly correlated with the star-formation surface density and the Clumpiness of the stellar light distribution. Galaxies with peculiar rest-frame UV / optical morphologies have comparable specific angular momentum to disc – dominated galaxies of the same stellar mass, but are clumpier and have higher star-formation rate surface densities. We propose that the peculiar morphologies in high–redshift systems are driven by higher star formation rate surface densities and higher gas fractions leading to a more clumpy inter-stellar medium.

Item Type:Article
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Publisher statement:This article has been accepted for publication in the Monthly notices of the Royal Astronomical Society ©: 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:18 December 2019
Date deposited:03 January 2020
Date of first online publication:23 December 2019
Date first made open access:03 January 2020

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