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23 April 2024 |
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An Increasing Stellar Baryon Fraction in Bright Galaxies at High Redshift | | Steven L. Finkelstein
; Mimi Song
; Peter Behroozi
; Rachel S. Somerville
; Casey Papovich
; Milos Milosavljevic
; Avishai Dekel
; Desika Narayanan
; Matthew L. N. Ashby
; Asantha Cooray
; Giovanni G. Fazio
; Henry C. Ferguson
; Anton M. Koekemoer
; Brett W. Salmon
; S. P. Willner
; | | Date: |
31 Mar 2015 | | Abstract: | Recent observations have shown that the characteristic luminosity of the
rest-frame ultraviolet (UV) luminosity function does not significantly evolve
at 4 < z < 7 and is approximately M*_UV ~ -21. We investigate this apparent
non-evolution by examining a sample of 190 bright, M_UV < -21 galaxies at z=4
to 7, analyzing their stellar populations and host halo masses. Including deep
Spitzer/IRAC imaging to constrain the rest-frame optical light, we find that
M*_UV galaxies at z=4-7 have similar stellar masses of log(M/Msol)=9.8-9.9 and
are thus relatively massive for these high redshifts. However, bright galaxies
at z=4-7 are less massive and have younger inferred ages than similarly bright
galaxies at z=2-3, even though the two populations have similar star formation
rates and levels of dust attenuation. We match the abundances of these bright
z=4-7 galaxies to halo mass functions from the Bolshoi Lambda-CDM simulation to
estimate the halo masses. We find that the typical halo masses in ~M*_UV
galaxies decrease from log(M_h/Msol)=11.9 at z=4 to log(M_h/Msol)=11.4 at z=7.
Thus, although we are studying galaxies at a similar mass across multiple
redshifts, these galaxies live in lower mass halos at higher redshift. The
stellar baryon fraction in units of the cosmic mean Omega_b/Omega_m rises from
6% at z=4 to 16% at z=7; this evolution is significant at the 3.6-sigma level.
This rise does not agree with simple expectations of how galaxies grow, and
implies that some effect, perhaps a diminishing efficiency of feedback, is
allowing a higher fraction of available baryons to be converted into stars at
high redshifts. | | Source: | arXiv, 1504.0005 | | Services: | Forum | Review | PDF | Favorites | |
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