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Title: THE MAJOR AND MINOR GALAXY MERGER RATES AT z < 1.5

Abstract

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){supmore » +0.1{+-}0.4}). We calculate the minor merger rate (1:4« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [7]
  1. National Optical Astronomical Observatories, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  3. Carnegie Observatories, Pasadena, CA (United States)
  4. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn (Australia)
  5. Department of Physics, University of California, Santa Cruz, CA (United States)
  6. Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)
  7. Jet Propulsion Laboratory, Pasadena, CA (United States)
Publication Date:
OSTI Identifier:
22004605
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 742; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMMETRY; GALACTIC EVOLUTION; GALAXIES; LUMINOSITY; MASS; MORPHOLOGY; RED SHIFT; SIMULATION

Citation Formats

Lotz, Jennifer M, Jonsson, Patrik, Cox, T J, Croton, Darren, Primack, Joel R, Somerville, Rachel S, and Stewart, Kyle. THE MAJOR AND MINOR GALAXY MERGER RATES AT z < 1.5. United States: N. p., 2011. Web. doi:10.1088/0004-637X/742/2/103.
Lotz, Jennifer M, Jonsson, Patrik, Cox, T J, Croton, Darren, Primack, Joel R, Somerville, Rachel S, & Stewart, Kyle. THE MAJOR AND MINOR GALAXY MERGER RATES AT z < 1.5. United States. https://doi.org/10.1088/0004-637X/742/2/103
Lotz, Jennifer M, Jonsson, Patrik, Cox, T J, Croton, Darren, Primack, Joel R, Somerville, Rachel S, and Stewart, Kyle. 2011. "THE MAJOR AND MINOR GALAXY MERGER RATES AT z < 1.5". United States. https://doi.org/10.1088/0004-637X/742/2/103.
@article{osti_22004605,
title = {THE MAJOR AND MINOR GALAXY MERGER RATES AT z < 1.5},
author = {Lotz, Jennifer M and Jonsson, Patrik and Cox, T J and Croton, Darren and Primack, Joel R and Somerville, Rachel S and Stewart, Kyle},
abstractNote = {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},
doi = {10.1088/0004-637X/742/2/103},
url = {https://www.osti.gov/biblio/22004605}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 742,
place = {United States},
year = {Thu Dec 01 00:00:00 EST 2011},
month = {Thu Dec 01 00:00:00 EST 2011}
}