THE MAJOR AND MINOR GALAXY MERGER RATES AT z < 1.5
- National Optical Astronomical Observatories, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States)
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
- Carnegie Observatories, Pasadena, CA (United States)
- Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn (Australia)
- Department of Physics, University of California, Santa Cruz, CA (United States)
- Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)
- Jet Propulsion Laboratory, Pasadena, CA (United States)
Calculating the galaxy merger rate requires both a census of galaxies identified as merger candidates and a cosmologically averaged 'observability' timescale (T{sub obs}(z)) for identifying galaxy mergers. While many have counted galaxy mergers using a variety of techniques, (T{sub obs}(z)) for these techniques have been poorly constrained. We address this problem by calibrating three merger rate estimators with a suite of hydrodynamic merger simulations and three galaxy formation models. We estimate (T{sub obs}(z)) for (1) close galaxy pairs with a range of projected separations, (2) the morphology indicator G - M{sub 20}, and (3) the morphology indicator asymmetry A. Then, we apply these timescales to the observed merger fractions at z < 1.5 from the recent literature. When our physically motivated timescales are adopted, the observed galaxy merger rates become largely consistent. The remaining differences between the galaxy merger rates are explained by the differences in the ranges of the mass ratio measured by different techniques and differing parent galaxy selection. The major merger rate per unit comoving volume for samples selected with constant number density evolves much more strongly with redshift ({proportional_to}(1 + z){sup +3.0{+-}1.1}) than samples selected with constant stellar mass or passively evolving luminosity ({proportional_to}(1 + z){sup +0.1{+-}0.4}). We calculate the minor merger rate (1:4
- OSTI ID:
- 22004605
- Journal Information:
- Astrophysical Journal, Vol. 742, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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