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CANDELS: The Evolution of Galaxy Rest-Frame Ultraviolet Colors from z = 8 to 4 | | Steven L. Finkelstein
; Casey Papovich
; Brett Salmon
; Kristian Finlator
; Mark Dickinson
; Henry C. Ferguson
; Mauro Giavalisco
; Anton M. Koekemoer
; Naveen A. Reddy
; Robert Bassett
; Christopher J. Conselice
; James S. Dunlop
; S. M. Faber
; Norman A. Grogin
; Nimish P. Hathi
; Dale D. Kocevski
; Kamson Lai
; Kyoung-Soo Lee
; Ross J. McLure
; Bahram Mobasher
; Jeffrey A. Newman
; | | Date: |
17 Oct 2011 | | Abstract: | We present an analysis of the rest-frame UV colors of galaxies at 4<z<8. We
use new wide-field NIR data in GOODS-S from CANDELS, as well as existing data
in the HUDF and ERS regions to select galaxies via their photometric redshifts.
Our sample consists of 2812 candidate galaxies, with 113 candidate galaxies at
z=7-8. We fit the observed SEDs to synthetic stellar population models and
measure the value of the rest-frame UV spectral slope beta from the best-fit
model spectrum. This results in a smaller average scatter on beta than other
methods. We compute a median value of beta and its associated uncertainty in
redshift bins from z=4-8, and we find that beta evolves significantly from
-1.83 +/- 0.02 at z=4, to -2.37 +0.28/-0.06 at z=7. Additionally, we find that
faint galaxies at z=7 have beta = -2.68 +0.44/-0.23 (~ -2.5 after correcting
for observational bias); this value does not require very-low metallicities in
these galaxies. This evolution can be explained by increased dust extinction,
from low amounts at z=7 to A_v~0.5 mag at z=4. This may be due to the increased
presence of low-mass AGB stars forming the bulk of the dust, as there is
insufficient time for the expected progenitors of M < 3 Msol AGB stars to
evolve off the main sequence at z>7. Finally, we examine whether there is any
correlation between beta and the UV luminosity or stellar mass. We find that
the existence of a correlation is highly dependent upon the definition of M_UV,
and we find no evidence for a significant correlation when measuring M_UV at
rest-frame 1500 A. We do find a strong correlation between beta and the stellar
mass, in that more massive galaxies exhibit redder colors. The most massive
galaxies have similarly red colors at all redshifts, implying that dust builds
up quickly in massive galaxies, and that feedback is likely removing
SNe-created dust from low-mass galaxies at z>7 [abridged]. | | Source: | arXiv, 1110.3785 | | Services: | Forum | Review | PDF | Favorites | |
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