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

## TL;DR

This study measures the rotational velocities and angular momentum of z~0.9 star-forming galaxies, revealing that their angular momentum-mass-morphology relationship is similar to local galaxies, despite lower angular momentum compared to present-day disks.

## Contribution

It provides the first large dynamical dataset for z~1 galaxies, showing that the angular momentum-mass-morphology relationship exists at this epoch and comparing angular momentum evolution.

## Key findings

- Rotation velocity-stellar mass relation similar to local disks.
- Specific angular momentum is 0.2-0.3 dex lower than in z=0 disks.
- Angular momentum scales with mass as M^{0.6±0.2}.

## Abstract

We present dynamical measurements for 586 H-alpha 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 Msol/yr and a stellar mass range of log[M/Msol]~9-11. We find that the rotation velocity-stellar mass relationship (the inverse of the Tully-Fisher relationship) for our rotationally-dominated sources (v/sigma>1) has a consistent slope and normalisation as that observed for z=0 disks. 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 disks. The specific angular momentum scales as M^[0.6+/-0.2], consistent with that expected for dark matter (i.e., proportional to M^[2/3]). We find that z~0.9 star-forming galaxies have decreasing specific angular momentum with increasing Sersic index. Visually, the sources with the highest specific angular momentum, for a given mass, have the most disk-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.