AEGIS: THE MORPHOLOGIES OF GREEN GALAXIES AT 0.4 < z < 1.2

Journal Article · Mon Aug 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/736/2/110· OSTI ID:21578247

Mendez, Alexander J; Coil, Alison L; Moustakas, John ^[1]; Lotz, Jennifer; Salim, Samir ^[2]; Simard, Luc ^[3]

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1. Department of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States)
2. National Optical Astronomical Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
3. National Research Council of Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, British Columbia V9E 2E7 (Canada)

We present quantitative morphologies of {approx}300 galaxies in the optically defined green valley at 0.4 < z < 1.2, in order to constrain the mechanism(s) responsible for quenching star formation in the bulk of this population. The sample is selected from galaxies in the All-Wavelength Extended Groth Strip International Survey (AEGIS). While the green valley is defined using optical U - B colors, we find that using a green valley sample defined using NUV - R colors does not change the results. Using Hubble Space Telescope/Advanced Camera for Surveys imaging, we study several quantitative morphological parameters including CAS, B/T from GIM2D, and Gini/M{sub 20}. We find that the green galaxy population is intermediate between the red and blue galaxy populations in terms of concentration, asymmetry, and morphological type and merger fraction estimated using Gini/M{sub 20}. We find that most green galaxies are not classified as mergers; in fact, the merger fraction in the green valley is lower than in the blue cloud. We show that at a given stellar mass, green galaxies have higher concentration values than blue galaxies and lower concentration values than red galaxies. Additionally, we find that 12% of green galaxies have B/T = 0 and 21% have B/T {<=} 0.05. Our results show that green galaxies are generally massive (M{sub *} {approx} 10{sup 10.5} M{sub sun}) disk galaxies with high concentrations. We conclude that major mergers are likely not the sole mechanism responsible for quenching star formation in this population and that either other external processes or internal secular processes play an important role both in driving gas toward the center of these galaxies and in quenching star formation.

• OSTI ID: 21578247
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 736; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
MORPHOLOGY
QUENCHING
STARS