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Stellar populations from spectroscopy of a large sample of quiescent galaxies at z > 1: Measuring the contribution of progenitor bias to early size growth

Belli, Sirio and Newman, Andrew B. and Ellis, Richard S. (2015) Stellar populations from spectroscopy of a large sample of quiescent galaxies at z > 1: Measuring the contribution of progenitor bias to early size growth. Astrophysical Journal, 799 (2). Art. No. 206. ISSN 0004-637X.

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We analyze the stellar populations of a sample of 62 massive (log M_∗/M_⊙ > 10.7) galaxies in the redshift range 1 < z < 1.6, with the main goal of investigating the role of recent quenching in the size growth of quiescent galaxies over the redshift range 1.25 < z < 2 where the apparent growth is particularly rapid. We demonstrate that our sample is not biased toward bright, compact, or young galaxies, and thus is representative of the overall quiescent population. Our high signal-to-noise ratio Keck LRIS spectra probe the rest-frame Balmer break region which contains important absorption line diagnostics of recent star formation activity. We show that improved measures of the various stellar population parameters, including the star-formation timescale τ, age and dust extinction, can be determined by fitting templates jointly to both our spectroscopic and broad-band photometric data. These parameter fits allow us to backtrack the evolving trajectory of individual galaxies on the UV J color-color plane. In addition to identifying which quiescent galaxies were recently quenched, an effect often termed progenitor bias in studies of the evolution of this population, we discover important variations in the star formation history of quiescent galaxies indicating the likelihood of more than one quenching route. By using sizes measured in the previous paper of this series, we confirm that the largest galaxies are indeed among the youngest at a given redshift, an effect consistent with some contribution to the apparent growth from recent arrivals. However, we calculate that recently-quenched objects can only be responsible for about half of the increase in the average size of quiescent galaxies over a 1.5 Gyr period corresponding to the redshift interval 1.25 < z < 2. The remainder of the observed size evolution arises from a genuine growth of long-standing quiescent galaxies. We discuss the prospects of determining whether the combination of minor merging and progenitor bias can explain the remarkably fast apparent growth rate during this short period of cosmic history.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Belli, Sirio0000-0002-5615-6018
Newman, Andrew B.0000-0001-7769-8660
Ellis, Richard S.0000-0001-7782-7071
Additional Information:© 2015 American Astronomical Society. Received 2014 September 24; accepted 2014 December 7; published 2015 January 30. We acknowledge Danilo Marchesini for useful discussions. 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, galaxies: stellar content
Issue or Number:2
Record Number:CaltechAUTHORS:20141015-141018925
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Official Citation:Stellar Populations from Spectroscopy of a Large Sample of Quiescent Galaxies at Z > 1: Measuring the Contribution of Progenitor Bias to Early Size Growth Sirio Belli et al. 2015 ApJ 799 206
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50417
Deposited By: Ruth Sustaita
Deposited On:15 Oct 2014 22:10
Last Modified:03 Oct 2019 07:23

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