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Velocity Dispersions and Dynamical Masses for a Large Sample of Quiescent Galaxies at z > 1: Improved Measures of the Growth in Mass and Size

Belli, Sirio and Newman, Andrew B. and Ellis, Richard S. (2014) Velocity Dispersions and Dynamical Masses for a Large Sample of Quiescent Galaxies at z > 1: Improved Measures of the Growth in Mass and Size. Astrophysical Journal, 783 (2). Art. No. 117. ISSN 0004-637X.

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We present Keck LRIS spectroscopy for a sample of 103 massive (M > 10^(10.6) M☉) galaxies with redshifts 0.9 < z < 1.6. Of these, 56 are quiescent with high signal-to-noise absorption line spectra, enabling us to determine robust stellar velocity dispersions for the largest sample yet available beyond a redshift of 1. Together with effective radii measured from deep Hubble Space Telescope images, we calculate dynamical masses and address key questions relating to the puzzling size growth claimed by many observers for quiescent galaxies over the redshift interval 0 < z < 2. Our large sample provides the first opportunity to carefully examine the relationship between stellar and dynamical masses at high redshift. We find this relation closely follows that determined locally. We also confirm the utility of the locally established empirical calibration which enables high-redshift velocity dispersions to be estimated photometrically, and we determine its accuracy to be 35%. To address recent suggestions that progenitor bias—the continued arrival of recently quenched larger galaxies—can largely explain the size evolution of quiescent galaxies, we examine the growth at fixed velocity dispersion assuming this quantity is largely unaffected by the merger history. Using the velocity dispersion-age relation observed in the local universe, we demonstrate that significant size and mass growth have clearly occurred in individual systems. Parameterizing the relation between mass and size growth over 0 < z < 1.6 as R ∝ M^α, we find α = 1.6 ± 0.3, in agreement with theoretical expectations from simulations of minor mergers. Relaxing the assumption that the velocity dispersion is unchanging, we examine growth assuming a constant ranking in galaxy velocity dispersion. This approach is applicable only to the large-dispersion tail of the distribution, but yields a consistent growth rate of α = 1.4 ± 0.2. Both methods confirm that progenitor bias alone is insufficient to explain our new observations and that quiescent galaxies have grown in both size and stellar mass over 0 < z < 1.6.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Belli, Sirio0000-0002-5615-6018
Newman, Andrew B.0000-0001-7769-8660
Ellis, Richard S.0000-0001-7782-7071
Additional Information:© 2014 The American Astronomical Society. Received 2013 November 13; accepted 2014 January 22; published 2014 February 21. We acknowledge Carrie Bridge and Kevin Bundy for completing the LRIS observations for two of the slitmasks. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Subject Keywords:galaxies: evolution; galaxies: fundamental parameters; galaxies: high-redshift; galaxies: structure
Issue or Number:2
Record Number:CaltechAUTHORS:20140617-090121553
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Official Citation:Velocity Dispersions and Dynamical Masses for a Large Sample of Quiescent Galaxies at z > 1: Improved Measures of the Growth in Mass and Size Sirio Belli et al. 2014 ApJ 783 117
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46297
Deposited By: Tony Diaz
Deposited On:17 Jun 2014 18:36
Last Modified:03 Oct 2019 06:43

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