A LARGE POPULATION OF MASSIVE COMPACT POST-STARBURST GALAXIES AT z > 1: IMPLICATIONS FOR THE SIZE EVOLUTION AND QUENCHING MECHANISM OF QUIESCENT GALAXIES

Journal Article · Wed Feb 01 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/745/2/179· OSTI ID:22011698

Whitaker, Katherine E; Van Dokkum, Pieter G; Bezanson, Rachel ^[1]; Kriek, Mariska ^[2]; Brammer, Gabriel ^[3]; Franx, Marijn; Labbe, Ivo ^[4]

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1. Department of Astronomy, Yale University, New Haven, CT 06511 (United States)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
3. European Southern Observatory, Alonso de Cordova 3107,Casilla 19001, Vitacura, Santiago (Chile)
4. Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands)

We study the growth of the red sequence through the number density and structural evolution of a sample of young and old quiescent galaxies at 0 < z < 2. The galaxies are selected from the NEWFIRM Medium-Band Survey in the Cosmic Evolution Survey field. We find a large population of massive young recently quenched ({sup p}ost-starburst{sup )} galaxies at z > 1 that are almost non-existent at z < 1; their number density is 5 Multiplication-Sign 10{sup -5} Mpc{sup -3} at z = 2, whereas it is a factor of 10 less at z = 0.5. The observed number densities of young and old quiescent galaxies at z > 1 are consistent with a simple model in which all old quiescent galaxies were once identified as post-starburst galaxies. We find that the overall population of quiescent galaxies have smaller sizes and slightly more elongated shapes at higher redshift, in agreement with other recent studies. Interestingly, the most recently quenched galaxies at 1 < z < 2 are not larger, and possibly even smaller, than older galaxies at those redshifts. This result is inconsistent with the idea that the evolution of the average size of quiescent galaxies is largely driven by continuous transformations of larger, star-forming galaxies: in that case, the youngest quiescent galaxies would also be the largest. Instead, mergers or other mechanisms appear to be required to explain the size growth of quiescent galaxies from z = 2 to the present.

• OSTI ID: 22011698
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 745; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DENSITY
GALACTIC EVOLUTION
GALAXIES
RED SHIFT
STARS