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A Close-pair Analysis of Damp Mergers at Intermediate Redshifts

Chou, Richard C. Y. and Bridge, Carrie R. and Abraham, Roberto G. (2012) A Close-pair Analysis of Damp Mergers at Intermediate Redshifts. Astrophysical Journal, 760 (2). Art. No. 113. ISSN 0004-637X. doi:10.1088/0004-637X/760/2/113.

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We have studied the kinematics of ~2800 candidate close-pair galaxies at 0.1 < z < 1.2 identified from the Canada-France-Hawaii Telescope Legacy Survey fields. Spectra of these systems were obtained using spectrometers on the 6.5 m Magellan and 5 m Hale telescopes. These data allow us to constrain the rate of dry mergers at intermediate redshifts and to test the "hot halo" model for quenching of star formation. Using virial radii estimated from the correlation between dynamical and stellar masses published by Leauthaud et al., we find that around 1/5 of our candidate pairs are likely to share a common dark matter halo (our metric for close physical association). These pairs are divided into red-red, blue-red, and blue-blue systems using the rest-frame colors classification method introduced in Chou et al.. Galaxies classified as red in our sample have very low star formation rates, but they need not be totally quiescent, and hence we refer to them as "damp," rather than "dry," systems. After correcting for known selection effects, the fraction of blue-blue pairs is significantly greater than that of red-red and blue-red pairs. Red-red pairs are almost entirely absent from our sample, suggesting that damp mergers are rare at z ~ 0.5. Our data support models with a short merging timescale (<0.5 Gyr) in which star formation is enhanced in the early phase of mergers, but quenched in the late phase. Hot halo models may explain this behavior, but only if virial shocks that heat gas are inefficient until major mergers are nearly complete.

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Abraham, Roberto G.0000-0002-4542-921X
Additional Information:© 2012 American Astronomical Society. Received 2012 April 24; accepted 2012 October 9; published 2012 November 14.
Subject Keywords:galaxies: evolution; galaxies: formation; galaxies: interactions
Issue or Number:2
Record Number:CaltechAUTHORS:20121219-122507868
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Official Citation:A Close-pair Analysis of Damp Mergers at Intermediate Redshifts Richard C. Y. Chou, Carrie R. Bridge, and Roberto G. Abraham doi:10.1088/0004-637X/760/2/113
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36052
Deposited By: Ruth Sustaita
Deposited On:19 Dec 2012 21:09
Last Modified:09 Nov 2021 23:19

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