The KMOS Redshift One Spectroscopic Survey (KROSS): rotational velocities and angular momentum of z ≈ 0.9 galaxies★
Smail, Ian; Jarvis, M. J.; Swinbank, A. M.; Cirasuolo, M.; Magdis, G.; Bower, R. G.; Bunker, A. J.; Sobral, D.; Harrison, C. M.; Best, P.; Bureau, M.; Johnson, H. L.; Tiley, A. L.; Stott, J. P.; Sharples, R. M.
United Kingdom, Germany, Japan, Netherlands, South Africa, Denmark, Greece
Abstract
We present dynamical measurements for 586 Hα-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 (vC/σ0 > 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_{\star }^{0.6± 0.2}, consistent with that expected for dark matter (I.e. j_DM∝ M_DM^{2/3}). We find that z ≈ 0.9 star-forming galaxies have decreasing specific angular momentum with increasing Sérsic 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.