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Keck Spectroscopy of z > 1 Field Spheroidals: Dynamical Constraints on the Growth Rate of Red "Nuggets"

Newman, Andrew B. and Ellis, Richard S. and Treu, Tommaso and Bundy, Kevin (2010) Keck Spectroscopy of z > 1 Field Spheroidals: Dynamical Constraints on the Growth Rate of Red "Nuggets". Astrophysical Journal Letters, 717 (2). L103-L107. ISSN 2041-8205.

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We present deep Keck spectroscopy for 17 morphologically selected field spheroidals in the redshift range 1.05 < z < 1.60 in order to investigate the continuity in physical properties between the claimed massive compact red galaxies ("nuggets") at z ≃ 2 and well-established data for massive spheroidal galaxies below z ≃ 1. By combining Keck-based stellar velocity dispersions with Hubble Space Telescope-based sizes, we find that the most massive systems (M_(dyn) > 10^(11) M_☉) grew in size over 0 < z < 1.6 as (1 + z)^(–0.75±0.10) (i.e., ×2 since z = 1.5) whereas intermediate mass systems (10^(11) M_☉ > M_(dyn) > 10^(10) M_☉) did not grow significantly. These trends are consistent with a picture in which more massive spheroidals formed at higher redshift via "wetter" mergers involving greater dissipation. To examine growth under the favored "dry" merger hypothesis, we also examine size growth at a fixed velocity dispersion. This test, uniquely possible with our dynamical data, allows us to consider the effects of "progenitor bias." Above our completeness limit (σ > 200 km s^(–1)), we find size growth consistent with that inferred for the mass-selected sample, thus ruling out strong progenitor bias. To maintain continuity in the growth of massive galaxies over the past 10 Gyr, our new results imply that size evolution over 1.3 < z < 2.3, a period of 1.9 Gyr, must have been even more dramatic than hitherto claimed if the red sources at z > 2 are truly massive and compact.

Item Type:Article
Related URLs:
URLURL TypeDescription
Newman, Andrew B.0000-0001-7769-8660
Ellis, Richard S.0000-0001-7782-7071
Treu, Tommaso0000-0002-8460-0390
Bundy, Kevin0000-0001-9742-3138
Additional Information:© 2010 American Astronomical Society. Received 2010 April 9; accepted 2010 June 4; published 2010 June 21. We thank Peter Capak for kindly providing photometric catalogs for the SSA22 field and Arjen van der Wel for helpful comments regarding size measurements. It is a pleasure to acknowledge Matt Auger for computing the stellar masses and Dan Stark for the DEIMOS observation. We thank the anonymous referee for comments that improved the quality of this Letter. We are grateful to the staff of the Keck Observatory and Connie Rockosi, in particular, for ensuring our early access to the upgraded LRIS-R was successful. Research support by the Packard Foundation is gratefully acknowledged by T.T. The authors recognize and acknowledge the cultural role and reverence that the summit ofMauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Funding AgencyGrant Number
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:galaxies: elliptical and lenticular; cD – galaxies: evolution
Issue or Number:2
Classification Code:PACS: 98.52.Eh; 98.62.Ai; 98.62.Lv; 95.85.Kr; 98.52.Lp; 98.62.Py
Record Number:CaltechAUTHORS:20100720-104323873
Persistent URL:
Official Citation:Andrew B. Newman et al 2010 ApJ 717 L103 doi: 10.1088/2041-8205/717/2/L103
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19125
Deposited By: Jason Perez
Deposited On:20 Jul 2010 18:18
Last Modified:23 Nov 2019 00:18

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