MAJOR-MERGER GALAXY PAIRS IN THE COSMOS FIELD-MASS-DEPENDENT MERGER RATE EVOLUTION SINCE z = 1
- Infrared Processing and Analysis Center, California Institute of Technology 100-22, Pasadena, CA 91125 (United States)
- Purple Mountain Observatory, Chinese Academy of Sciences, 2 West Beijing Road, Nanjing 210008 (China)
- California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
- Spitzer Science Center, California Institute of Technology, Mail Stop 220-6, Pasadena, CA 91125 (United States)
- Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, A.P. 70-264, 04510 Mexico, D.F. (Mexico)
We present results of a statistical study of the cosmic evolution of the mass-dependent major-merger rate since z = 1. A stellar mass limited sample of close major-merger pairs (the CPAIR sample) was selected from the archive of the COSMOS survey. Pair fractions at different redshifts derived using the CPAIR sample and a local K-band-selected pair sample show no significant variations with stellar mass. The pair fraction exhibits moderately strong cosmic evolution, with the best-fitting function of f{sub pair} = 10{sup -1.88({+-}0.03)}(1 + z){sup 2.2({+-}0.2)}. The best-fitting function for the merger rate is R{sub mg} (Gyr{sup -1}) = 0.053 Multiplication-Sign (M{sub star}/10{sup 10.7} M{sub Sun} ){sup 0.3}(1 + z){sup 2.2}/(1 + z/8). This rate implies that galaxies of M{sub star} {approx} 10{sup 10}-10{sup 11.5} M{sub Sun} have undergone {approx}0.5-1.5 major mergers since z = 1. Our results show that, for massive galaxies (M{sub star} {>=} 10{sup 10.5} M{sub Sun }) at z {<=} 1, major mergers involving star-forming galaxies (i.e., wet and mixed mergers) can account for the formation of both ellipticals and red quiescent galaxies (RQGs). On the other hand, major mergers cannot be responsible for the formation of most low mass ellipticals and RQGs of M{sub star} {approx}< 10{sup 10.3} M{sub Sun }. Our quantitative estimates indicate that major mergers have significant impact on the stellar mass assembly of the most massive galaxies (M{sub star} {>=} 10{sup 11.3} M{sub Sun }), but for less massive galaxies the stellar mass assembly is dominated by the star formation. Comparison with the mass-dependent (ultra)luminous infrared galaxies ((U)LIRG) rates suggests that the frequency of major-merger events is comparable to or higher than that of (U)LIRGs.
- OSTI ID:
- 22016270
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 747; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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