The KMOS Redshift One Spectroscopic Survey (KROSS): rotational velocities and angular momentum of z ≈ 0.9 galaxies★

We present dynamical measurements for 586 H-detected star-forming galaxies from the KMOS (K-band Multi-Object Spectrograph) Redshift One Spectroscopic Survey (KROSS). The sample represents typical star-forming galaxies at this redshift (z = 0.6-1.0), with a median star formation rate of 7 M yr -1 and a stellar mass range of log (M M ) 9-11. We find that the rotation velocity-stellar mass relationship (the inverse of the Tully-Fisher relationship) for our rotationally dominated sources (v C / 0 > 1) has a consistent slope and normalization as that observed for z = 0 discs. In contrast, the specific angular momentum (j ; angular momentum divided by stellar mass) is 0.2-0.3 dex lower on average compared to z = 0 discs. The specific angular momentum scales as j s M 0.60.2 , consistent with that expected for dark matter (i.e. j DM M 2/3 DM ). We find that z 0.9 star-forming galaxies have decreasing specific angular momentum with increasing Srsic index. Visually, the sources with the highest specific angular momentum, for a given mass, have the most disc-dominated morphologies. This implies that an angular momentum-mass-morphology relationship, similar to that observed in local massive galaxies, is already in place by z 1.