Abstract

We present an analysis of the gas dynamics of star-forming galaxies at z similar to 1.5 using data from the KMOS Galaxy Evolution Survey. We quantify the morphology of the galaxies using HST CANDELS imaging parametrically and non-parametrically. We combine the Ha dynamics from KMOS with the high-resolution imaging to derive the relation between stellar mass (M-*) and stellar specific angular momentum (j(*)). We showthat high-redshift star-forming galaxies at z similar to 1.5 followa power-lawtrend in specific stellar angular momentum with stellarmass similar to that of local late-type galaxies of the form j(*) proportional to M-*(0.53 +/- 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 scatterwithin the j(*) - M-* plane and its correlationwith both the integrated dynamical properties of a galaxy (e.g. velocity dispersion, Toomre Q(g), H alpha star formation rate surface density Sigma(SFR)) and its parametrized rest-frame UV/optical morphology (e.g. Sersic 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 interstellar medium.