The Evolution of the Galaxy Stellar Mass Function at z = 4-8: A Steepening Low-mass-end Slope with Increasing Redshift
Journal
Date Issued
2016
Author(s)
Song, Mimi
•
Finkelstein, Steven L.
•
Ashby, Matthew L. N.
•
•
Lu, Yu
•
Papovich, Casey
•
Salmon, Brett
•
Somerville, Rachel S.
•
•
Duncan, K.
•
Faber, Sandy M.
•
Fazio, Giovanni G.
•
Ferguson, Henry C.
•
•
Guo, Yicheng
•
Hathi, Nimish
•
Lee, Seong-Kook
•
•
Willner, S. P.
Abstract
We present galaxy stellar mass functions (GSMFs) at z = 4-8 from a rest-frame ultraviolet (UV) selected sample of ∼4500 galaxies, found via photometric redshifts over an area of ∼280 arcmin2 in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS)/Great Observatories Origins Deep Survey (GOODS) fields and the Hubble Ultra Deep Field. The deepest Spitzer/IRAC data to date and the relatively large volume allow us to place a better constraint at both the low- and high-mass ends of the GSMFs compared to previous space-based studies from pre-CANDELS observations. Supplemented by a stacking analysis, we find a linear correlation between the rest-frame UV absolute magnitude at 1500 Å ({M}{{UV}}) and logarithmic stellar mass ({log}{M}* ) that holds for galaxies with {log}({M}* /{M}☉ )≲ 10. We use simulations to validate our method of measuring the slope of the {log}{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 toward lower masses at higher redshift. We combine the {log}{M}* -M UV distribution with observed rest-frame UV luminosity functions at each redshift to derive the GSMFs, finding that the low-mass-end slope becomes steeper with increasing redshift from α =-{1.55}-0.07+0.08 at z = 4 to α =-{2.25}-0.35+0.72 at z = 8. The inferred stellar mass density, when integrated over {M}* ={10}8-1013 M ☉, increases by a factor of {10}-2+30 between z = 7 and z = 4 and is in good agreement with the time integral of the cosmic star formation rate density.
Volume
825
Issue
1
Start page
5
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...825....5S
Rights
open.access
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