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Galaxy pairs in deep HST images: Evidence for evolution in the galaxy merger rateWe use four deep serendipitous fields observed with the Hubble Space Telescope (HST) Wide-Field Camera to constrain the rate of galaxy merging between the current epoch and z approximately equals 0.7. Since most mergers occur between members of bound pairs, the merger rate is given to a good approximation by (half) the rate of disappearance of galaxies in pairs. An objective criterion for pair membership shows that 34% +/- 9% of our HST galaxies with I = 18-22 belong to pairs, compared to 7% locally. This means that about 13% of the galaxy population has disappeared due to merging in the cosmic epoch corresponding to this magnitude interval (or 0.1 approximately less than z approximately less than 0.7). Our pair fraction is a lower limit: correction for pair members falling below our detection threshold might raise the fraction to approximately 50%. Since we address only two-galaxy merging, these values do not include physical systems of higher multiplicity. Incorporating I-band field-galaxy redshift distributions, the pair fraction grows with redshift as alpha(1 + z)(exp 3.5 +/- 0.5) and the merger rate as (1 + z)(exp 2.5 +/- 0.5). This may have significant implications for the interpretation of galaxy counts (disappearance of faint blue galaxies), the cosmological evolution of faint radio sources and quasars (which evolve approximately as (1 + z)(exp 3), the similarity in the power law is necessary but not sufficient evidence for a causal relation), statistics of QSO companions, the galaxy content in distant clusters, and the merging history of a 'typical' galaxy.
Document ID
19950029683
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Burkey, Jordan M.
(Univ. of Alabama, Tuscaloosa, AL United States)
Keel, William C.
(Univ. of Alabama, Tuscaloosa, AL United States)
Windhorst, Rogier A.
(Arizona State Univ. Tempe, AZ, United States)
Franklin, Barbara E.
(Arizona State Univ. Tempe, AZ, United States)
Date Acquired
August 16, 2013
Publication Date
July 1, 1994
Publication Information
Publication: The Astrophysical Journal
Volume: 429
Issue: 1 pt
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A61282
Funding Number(s)
CONTRACT_GRANT: NAG5-26555
Distribution Limits
Public
Copyright
Other

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