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Published November 21, 2007 | Published
Journal Article Open

Strong size evolution of the most massive galaxies since z ~ 2

Abstract

Using the combined capabilities of the large near-infrared Palomar/DEEP-2 survey, and the superb resolution of the Advanced Camera for Surveys HST camera, we explore the size evolution of 831 very massive galaxies (M_⋆ ≥ 10^(11)h^(−2)_(70) M_⊙) since z ~ 2. We split our sample according to their light concentration using the Sérsic index n. At a given stellar mass, both low (n < 2.5) and high (n > 2.5) concentrated objects were much smaller in the past than their local massive counterparts. This evolution is particularly strong for the highly concentrated (spheroid like) objects. At z ~ 1.5, massive spheroid-like objects were a factor of 4 (±0.4) smaller (i.e. almost two orders of magnitudes denser) than those we see today. These small sized, high-mass galaxies do not exist in the nearby Universe, suggesting that this population merged with other galaxies over several billion years to form the largest galaxies we see today.

Additional Information

© 2007 The Authors. Journal compilation © 2007 RAS. Accepted 2007 August 25; received 2007 July 24; in original form 2007 May 10. Published Online: 26 Oct 2007. Authors are grateful to M. Barden and D. McIntosh for providing us with the GEMS data points to allow us a comparison of our results with their less massive galaxies.We acknowledge useful discussions with O. Almaini and A. Arag´on-Salamanca.We also thank the useful suggestions from an anonymous referee. The Palomar and DEEP-2 surveys would not have been completed without the active help of the staff at the Palomar and Keck observatories. The Palomar Survey was supported by NSF grant AST-0307859 and NASA STScI grant HST- AR-09920.01.A. Support for the ACS imaging of the EGS in GO program 10134 was provided by NASA through NASA grant HST-GO-10134.13-A from the Space Telescope Science Institute.

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August 22, 2023
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