Angular momentum of z ∼ 1.5 galaxies and their local analogues with adaptive optics.

Abstract

We present stellar specific angular momentum j* measurements of two z ∼ 1.5 galaxies in the KGES sample and 12 DYNAMO z ∼ 0.1 analogues of high-redshift galaxies. We combine natural seeing integral field spectroscopic data to trace line emission out to high multiples of effective radius re, with adaptive optics assisted Keck/OSIRIS observations to trace the rapid rise in rotation curve in the inner regions. Our spaxel-wise integration method gives results that are on average within measurement uncertainty of the traditional rotation curve model method. At z ∼ 0, combining GMOS and OSIRIS datasets improves the measurement uncertainty in j* from 13% (GMOS only) or 16% (OSIRIS only) to 10%. At z ∼ 1.5, systematics allow for at best 20% uncertainty on j*. DYNAMO analogues of high-z galaxies have low j* for their stellar mass M*, and low bulge-to-total light ratio β for their j*/M*. The high-z galaxy COSMOS 127977 has j*/M* consistent with normal local disk galaxies, while UDS 78317 is consistent with local analogues. However, our high-resolution OSIRIS data reveal that UDS 78317 may be a merging system. We report a relationship between distance to the β − j*/M* plane and the ratio of velocity dispersion to rotational velocity σ/vmax, where galaxies that deviate more from the plane are more dispersion-dominated due to turbulence. Much of the scatter in M* − j* that is not explained by variations in the bulge-to-total ratio or evolution with redshift may be driven by increased turbulence due to star formation, or by treating mergers as rotating disks.