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The Evolution of the Galaxy Stellar Mass Function at z= 4-8: A Steepening Low-mass-end Slope with Increasing Redshift | Mimi Song
; Steven L. Finkelstein
; Matthew L. N. Ashby
; A. Grazian
; Yu Lu
; Casey Papovich
; Brett Salmon
; Rachel S. Somerville
; Mark Dickinson
; K. Duncan
; Sandy M. Faber
; Giovanni G. Fazio
; Henry C. Ferguson
; Adriano Fontana
; Yicheng Guo
; Nimish Hathi
; Seong-Kook Lee
; Emiliano Merlin
; S. P. Willner
; | Date: |
20 Jul 2015 | Abstract: | We present galaxy stellar mass functions (GSMFs) at $z=$ 4-8 from a
rest-frame ultraviolet (UV) selected sample of $sim$4,500 galaxies, found via
photometric redshifts over an area of $sim$280 arcmin$^2$ in the CANDELS/GOODS
fields and the Hubble Ultra Deep Field. The deepest Spitzer/IRAC data
yet-to-date from the Spitzer-CANDELS (26.5 mag, 3$sigma$) and the IRAC Ultra
Deep Field 2010 (26.4-27.1 mag, 3$sigma$) surveys allow us to place robust
constraints on the low-mass-end slope of the GSMFs, while the relatively large
volume provides a better constraint at higher masses compared to previous
space-based studies. Supplemented by a stacking analysis, we find a linear
correlation between the rest-frame UV absolute magnitude at 1500AA ($M_{
m
UV}$) and logarithmic stellar mass ($log M_*$). We use simulations to validate
our method of measuring the slope of the $log M_*$-$M_{
m UV}$ relation,
finding that the bias is minimized with a hybrid technique combining photometry
of individual bright galaxies with stacked photometry for faint galaxies. The
resultant measured slopes do not significantly evolve over $z=$ 4-8, while the
normalization of the trend exhibits a weak evolution towards lower masses at
higher redshift for galaxies at fixed $M_{
m UV}$. We combine the $log
M_*$-$M_{
m UV}$ distribution with observed rest-frame UV luminosity functions
at each redshift to derive the GSMFs. While we see no evidence of an evolution
in the characteristic mass $M^*$, we find that the low-mass-end slope becomes
steeper with increasing redshift from $alpha=-1.53^{+0.07}_{-0.06}$ at $z=4$
to $alpha=-2.45^{+0.34}_{-0.29}$ at $z=8$. The inferred stellar mass density,
when integrated over $M_*=10^8$-$10^{13} M_{odot}$, increases by a factor of
$13^{+35}_{-9}$ between $z=7$ and $z=4$ and is in good agreement with the time
integral of the cosmic star-formation rate density. | Source: | arXiv, 1507.5636 | Services: | Forum | Review | PDF | Favorites |
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