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

Gillman, S.; Tiley, A.L.; Swinbank, A.M.; Harrison, C.M.; Smail, I.; Dudzevičiūtė, U; Sharples, R.M.; Cortese, L.; Obreschkow, D.; Bower, R.G.; Theuns, T.; Cirasuolo, M.; Fisher, D.B.; Glazebrook, K.; Ibar, E.; Mendel, J.T.; Sweet, S.M.

Abstract

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.

Citation

Gillman, S., Tiley, A., Swinbank, A., Harrison, C., Smail, I., Dudzevičiūtė, U., …Sweet, S. (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), 1492-1512. https://doi.org/10.1093/mnras/stz3576

• Journal Article Type: Article
• Acceptance Date: Dec 18, 2019
• Online Publication Date: Dec 23, 2019
• Publication Date: Feb 28, 2020
• Deposit Date: Dec 12, 2019
• Publicly Available Date: Jan 3, 2020
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 492
• Issue: 1
• Pages: 1492-1512
• DOI: https://doi.org/10.1093/mnras/stz3576