Spatially Resolved Stellar Kinematics from LEGA-C: Increased Rotational Support in z ∼ 0.8 Quiescent Galaxies
Journal
Astrophysical Journal
Journal Volume
858
Journal Issue
1
Date Issued
2018
Author(s)
Bezanson R
Van Der Wel A
Pacifici C
Noeske K
Barišić I
Bell E.F
Brammer G.B
Calhau J
Chauke P
Van Dokkum P
Franx M
Gallazzi A
Van Houdt J
Labbé I
Maseda M.V
Munos-Mateos J.C
Muzzin A
Van De Sande J
Sobral D
Straatman C
Abstract
We present stellar rotation curves and velocity dispersion profiles for 104 quiescent galaxies at z = 0.6-1 from the Large Early Galaxy Astrophysics Census (LEGA-C) spectroscopic survey. Rotation is typically probed across 10-20 kpc, or to an average of 2.7Re. Combined with central stellar velocity dispersions (σ0) this provides the first determination of the dynamical state of a sample selected by a lack of star formation activity at large lookback time. The most massive galaxies (M∗ > 2 ×1011 Mo) generally show no or little rotation measured at 5 kpc ( in eight of ten cases), while ∼64% of less massive galaxies show significant rotation. This is reminiscent of local fast- and slow-rotating ellipticals and implies that low- and high-redshift quiescent galaxies have qualitatively similar dynamical structures. We compare distributions at z ∼ 0.8 and the present day by re-binning and smoothing the kinematic maps of 91 low-redshift quiescent galaxies from the Calar Alto Legacy Integral Field Area (CALIFA) survey and find evidence for a decrease in rotational support since z ∼ 1. This result is especially strong when galaxies are compared at fixed velocity dispersion; if velocity dispersion does not evolve for individual galaxies then the rotational velocity at 5 kpc was an average of 94 ±22% higher in z ∼ 0.8 quiescent galaxies than today. Considering that the number of quiescent galaxies grows with time and that new additions to the population descend from rotationally supported star-forming galaxies, our results imply that quiescent galaxies must lose angular momentum between z ∼ 1 and the present, presumably through dissipationless merging, and/or that the mechanism that transforms star-forming galaxies also reduces their rotational support. © 2018. The American Astronomical Society. All rights reserved.
Subjects
galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: high-redshift; galaxies: kinematics and dynamics; galaxies: structure
Type
journal article