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Can Minor Merging Account for the Size Growth of Quiescent Galaxies? New Results from the CANDELS Survey

Newman, Andrew B. and Ellis, Richard S. and Bundy, Kevin and Treu, Tommaso (2012) Can Minor Merging Account for the Size Growth of Quiescent Galaxies? New Results from the CANDELS Survey. Astrophysical Journal, 746 (2). Art. 162. ISSN 0004-637X. doi:10.1088/0004-637X/746/2/162.

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The presence of extremely compact galaxies at z ~ 2 and their subsequent growth in physical size has been the cause of much puzzlement. We revisit the question using deep infrared Wide Field Camera 3 data to probe the rest-frame optical structure of 935 galaxies selected with 0.4 < z < 2.5 and stellar masses M_* > 10^(10.7) M_☉ in the UKIRT Ultra Deep Survey and GOODS-South fields of the CANDELS survey. At each redshift, the most compact sources are those with little or no star formation, and the mean size of these systems at fixed stellar mass grows by a factor of 3.5 ± 0.3 over this redshift interval. The data are sufficiently deep to identify companions to these hosts whose stellar masses are ten times smaller. By searching for these around 404 quiescent hosts within a physical annulus 10 h^(–1) kpc < R < 30 h^(–1) kpc, we estimate the minor merger rate over 0.4 < z < 2. We find that 13%-18% of quiescent hosts have likely physical companions with stellar mass ratios of 0.1 or greater. Mergers of these companions will typically increase the host mass by 6% ± 2% per merger timescale. We estimate the minimum growth rate necessary to explain the declining abundance of compact galaxies. Using a simple model motivated by recent numerical simulations, we then assess whether mergers of the faint companions with their hosts are sufficient to explain this minimal rate. We find that mergers may explain most of the size evolution observed at z lsim 1 if a relatively short merger timescale is assumed, but the rapid growth seen at higher redshift likely requires additional physical processes.

Item Type:Article
Related URLs:
URLURL TypeDescription
Newman, Andrew B.0000-0001-7769-8660
Ellis, Richard S.0000-0001-7782-7071
Bundy, Kevin0000-0001-9742-3138
Treu, Tommaso0000-0002-8460-0390
Additional Information:© 2012 American Astronomical Society. Received 2011 October 7; accepted 2012 January 6; published 2012 February 2. We thank Carlo Nipoti and Anna Nierenberg for fruitful conversations and useful comments, as well as the anonymous referee for a helpful report. This work is based on observations taken by the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. T.T. thanks the Packard Foundation for their support through a Packard Fellowship.
Funding AgencyGrant Number
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords: galaxies: evolution; galaxies: formation; galaxies: fundamental parameters; galaxies: structure
Issue or Number:2
Record Number:CaltechAUTHORS:20120327-151529899
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Official Citation: Can Minor Merging Account for the Size Growth of Quiescent Galaxies? New Results from the CANDELS Survey Andrew B. Newman et al. 2012 ApJ 746 162
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:29866
Deposited By: Ruth Sustaita
Deposited On:27 Mar 2012 22:54
Last Modified:09 Nov 2021 19:31

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