The Evolution of Galaxy Mergers and Morphology at z < 1.2 in the Extended Groth Strip

We present the quantitative rest-frame B morphological evolution and galaxy merger fraction at 0.2 < z < 1.2 as observed by the All-Wavelength Extended Groth Strip International Survey (AEGIS). We use the Gini coefficient and M sub(20) to identify major mergers and classify galaxy morphology f...

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Bibliographic Details
Published in:	The Astrophysical journal 2008-01, Vol.672 (1), p.177-197
Main Authors:	Lotz, Jennifer M, Davis, M, Faber, S. M, Guhathakurta, P, Gwyn, S, Huang, J, Koo, D. C, Le Floc’h, E, Lin, Lihwai, Newman, J, Noeske, K, Papovich, C, Willmer, C. N. A, Coil, A, Conselice, C. J, Cooper, M, Hopkins, A. M, Metevier, A, Primack, J, Rieke, G, Weiner, B. J
Format:	Article
Language:	eng
Subjects:	Astronomy Astrophysics Earth, ocean, space Exact sciences and technology Physics
Online Access:	Get full text
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Summary:	We present the quantitative rest-frame B morphological evolution and galaxy merger fraction at 0.2 < z < 1.2 as observed by the All-Wavelength Extended Groth Strip International Survey (AEGIS). We use the Gini coefficient and M sub(20) to identify major mergers and classify galaxy morphology for a volume-limited sample of 3009 galaxies brighter than 0.4L super(*) sub(B), assuming pure luminosity evolution. We find that the merger fraction remains roughly constant at 10% plus or minus 2% for 0.2 < z < 1.2. The fraction of E/S0/Sa galaxies increases from 21% plus or minus 3% at z similar to 1.1 to 44% plus or minus 9% at z similar to 0.3, while the fraction of Sb-Ir galaxies decreases from 64% plus or minus 6% at z similar to 1.1 to 47% similar to 9% at z similar to 0.3. The majority of z < 1.2 Spitzer MIPS 24 mu m sources with L(IR) > 10 super(11) L [unk] are disk galaxies, and only similar to 15% are classified as major merger candidates. Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequence at z similar to 1.1, while E/S0/Sa make up over 90% of the red sequence at z similar to 0.3. Approximately 2% of our full sample are red mergers. We conclude (1) the merger rate does not evolve strongly between 0.2 < z < 1.2; (2) the decrease in the volume-averaged star formation rate density since z similar to 1 is a result of declining star formation in disk galaxies rather than a disappearing population of major mergers; (3) the build-up of the red sequence at z < 1 can be explained by a doubling in the number of spheroidal galaxies since z similar to 1.2.
ISSN:	0004-637X 1538-4357