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A consistent measure of the merger histories of massive galaxies using close-pair statistics I: Major mergers at $z < 3.5$ | | Carl J. Mundy
; Christopher J. Conselice
; Kenneth J. Duncan
; Omar Almaini
; Boris Häußler
; William G. Hartley
; | | Date: |
22 May 2017 | | Abstract: | We use a large sample of $sim 350,000$ galaxies constructed by combining the
UKIDSS UDS, VIDEO/CFHT-LS, UltraVISTA/COSMOS and GAMA survey regions to probe
the major merging histories of massive galaxies ($>10^{10} mathrm{M}_odot$)
at $0.005 < z < 3.5$. We use a method adapted from that presented in
Lopez-Sanjuan et al. (2014) using the full photometric redshift probability
distributions, to measure pair $ extit{fractions}$ of flux-limited, stellar
mass selected galaxy samples using close-pair statistics. The pair fraction is
found to weakly evolve as $propto (1+z)^{0.8}$ with no dependence on stellar
mass. We subsequently derive major merger $ extit{rates}$ for galaxies at $>
10^{10} mathrm{M}_odot$ and at a constant number density of $n > 10^{-4}$
Mpc$^{-3}$, and find rates a factor of 2-3 smaller than previous works,
although this depends strongly on the assumed merger timescale and likelihood
of a close-pair merging. Galaxies undergo approximately 0.5 major mergers at $z
< 3.5$, accruing an additional 1-4 $ imes 10^{10} mathrm{M}_odot$ in the
process. Major merger accretion rate densities of $sim 2 imes 10^{-4}$
$mathrm{M}_odot$ yr$^{-1}$ Mpc$^{-3}$ are found for number density selected
samples, indicating that direct progenitors of local massive
($>10^{11}mathrm{M}_odot$) galaxies have experienced a steady supply of
stellar mass via major mergers throughout their evolution. While pair fractions
are found to agree with those predicted by the Henriques et al. (2014)
semi-analytic model, the Illustris hydrodynamical simulation fails to
quantitatively reproduce derived merger rates. Furthermore, we find major
mergers become a comparable source of stellar mass growth compared to
star-formation at $z < 1$, but is 10-100 times smaller than the SFR density at
higher redshifts. | | Source: | arXiv, 1705.7986 | | Services: | Forum | Review | PDF | Favorites | |
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