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Published February 1, 2012 | Published
Journal Article Open

Early-type Galaxies at z ~ 1.3. IV. Scaling Relations in Different Environments


We present the Kormendy and mass-size relations (MSR) for early-type galaxies (ETGs) as a function of environment at z ~ 1.3. Our sample includes 76 visually classified ETGs with masses 10^(10) < M/M_☉ < 10^(11.5), selected in the Lynx supercluster and in the Great Observatories Origins Deep Survey/Chandra Deep Field South field; 31 ETGs in clusters, 18 in groups, and 27 in the field, all with multi-wavelength photometry and Hubble Space Telescope/Advanced Camera for Surveys observations. The Kormendy relation, in place at z ~ 1.3, does not depend on the environment. The MSR reveals that ETGs overall appear to be more compact in denser environments: cluster ETGs have sizes on average around 30%-50% smaller than those of the local universe and a distribution with a smaller scatter, whereas field ETGs show an MSR with a similar distribution to the local one. Our results imply that (1) the MSR in the field did not evolve overall from z ~ 1.3 to present; this is interesting and in contrast to the trend found at higher masses from previous works; (2) in denser environments, either ETGs have increased in size by 30%-50% on average and spread their distributions, or more ETGs have been formed within the dense environment from non-ETG progenitors, or larger galaxies have been accreted to a pristine compact population to reproduce the MSR observed in the local universe. Our results are driven by galaxies with masses M lsim 2 × 10^(11) M_☉ and those with masses M ~ 10^(11) M_☉ follow the same trends as that of the entire sample. Following the Valentinuzzi et al. definition of superdense ETGs, ~35%-45% of our cluster sample is made up of superdense ETGs.

Additional Information

© 2012 American Astronomical Society. Received 2011 April 21; accepted 2011 September 29; published 2012 January 10. ACS was developed under NASA contract NAS 5-32865. This research has been supported by the NASA HST grant GO-10574.01-A, and Spitzer grant for program 20694. The Space Telescope Science Institute is operated by AURA Inc., under NASA contract NAS5-26555. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. 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. Some data were based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONlCYT (Chile), the Australian Research Council (Australia), Ministrio da Cincia e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnologa e lnnovacin Productiva (Argentina), Gemini Science Program ID: GN-2006A-Q-78. We thank the anonymous referee for a careful reading of the manuscript. A.R. thanks A. Graham for useful comments. Facilities: HST (ACS), Spitzer (IRAC), KPNO:2.1m (FLAMINGOS), Hale (COSMIC), Keck:I (LRIS), Gemini:Gillett (GMOS)

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