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Title: MAGAZ3NE: High Stellar Velocity Dispersions for Ultramassive Quiescent Galaxies at z ≳ 3*
Abstract In this work, we publish stellar velocity dispersions, sizes, and dynamical masses for eight ultramassive galaxies (UMGs; log ( M * / M ⊙ ) > 11), z ≳ 3) from the Massive Ancient Galaxies At z > 3 NEar-infrared (MAGAZ3NE) Survey, more than doubling the number of such galaxies with velocity dispersion measurements at this epoch. Using the deep Keck/MOSFIRE and Keck/NIRES spectroscopy of these objects in the H and K bandpasses, we obtain large velocity dispersions of ∼400 km s −1 for most of the objects, which are some of the highest stellar velocity dispersions measured and ∼40% larger than those measured for galaxies of similar mass at z ∼ 1.7. The sizes of these objects are also smaller by a factor of 1.5–3 compared to this same z ∼ 1.7 sample. We combine these large velocity dispersions and small sizes to obtain dynamical masses. The dynamical masses are similar to the stellar masses of these galaxies, consistent with a Chabrier initial mass function (IMF). Considered alongside previous studies of massive quiescent galaxies across 0.2 < z < 4.0, there is evidence for an evolution in the relation between the dynamical mass–stellar mass ratio and velocity dispersion as a function of redshift. This implies an IMF with fewer low-mass stars (e.g., Chabrier IMF) for massive quiescent galaxies at higher redshifts in conflict with the bottom-heavy IMF (e.g., Salpeter IMF) found in their likely z ∼ 0 descendants, though a number of alternative explanations such as a different dynamical structure or significant rotation are not ruled out. Similar to data at lower redshifts, we see evidence for an increase of IMF normalization with velocity dispersion, though the z ≳ 3 trend is steeper than that for z ∼ 0.2 early-type galaxies and offset to lower dynamical-to-stellar mass ratios.  more » « less
Award ID(s):
1908422 2009442 2347348
PAR ID:
10438253
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
938
Issue:
2
ISSN:
0004-637X
Page Range / eLocation ID:
109
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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