Resolving the discrepancy of galaxy merger fraction measurements at z ∼ 0-3

Journal Article · Thu Oct 20 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/830/2/89· OSTI ID:22868586

Man, Allison W. S.; Zirm, Andrew W.; Toft, Sune ^[1]

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1. Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen (Denmark)

We measure the merger fraction of massive galaxies using the UltraVISTA/COSMOS catalog, complemented with the deeper, higher resolution 3DHST+CANDELS catalog, presenting the largest mass-complete photometric merger sample up to z∼3. We find that the variation in the mass ratio probe can explain the discrepant redshift evolution of the merger fraction in the literature: selecting mergers using the H {sub 160}-band flux ratio leads to an increasing merger fraction with redshift, while selecting mergers using the stellar mass ratio reveals a merger fraction with little redshift dependence at z=1--3. Defining major and minor mergers as having stellar mass ratios of 1:1–4:1 and 4:1–10:1, respectively, the results imply ∼1 major merger and ∼0.7 minor merger on average for a massive (log (M{sub ⋆}/M{sub ⊙})⩾10.8) galaxy during z=0.1--2.5. There may be an additional ∼0.5(0.4) major (minor) merger if we use the H-band flux ratio selection. The observed amount of major merging alone is sufficient to explain the observed number density evolution for the very massive (log (M{sub ⋆}/M{sub ⊙})⩾11.1) galaxies. The observed number of major and minor mergers can increase the size of a massive quiescent galaxy by a factor of two at most. This amount of merging is enough to bring the compact quiescent galaxies formed at z>2 to lie at 1.5σ below the mean of the stellar mass–size relation as measured in some works (e.g., Newman et al.), but additional mechanisms are needed to fully explain the evolution, and to be consistent with works suggesting stronger evolution.

• OSTI ID: 22868586
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 830; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CATALOGS
DENSITY
GALACTIC EVOLUTION
GALAXIES
INTERACTIONS
MASS
RED SHIFT
RESOLUTION
STATISTICS