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

Sarah M. Sweet, Deanne B. Fisher, Giulia Savorgnan, Karl Glazebrook, Danail Obreschkow, Steven Gillman, Alfred L. Tiley, Claudia D.P. Lagos, Liang Wang, A. Mark Swinbank, Richard Bower, Ray M. Sharples

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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 data sets improves the measurement uncertainty in j from 13 per cent (GMOS only) or 16 per cent (OSIRIS only) to 10 per cent. At z ∼ 1.5, systematics allow for at best 20 per cent 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 disc 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 discs.

Original languageEnglish
Pages (from-to)5700-5714
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume485
Issue number4
DOIs
Publication statusPublished - 14 Mar 2019

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