TY - JOUR
T1 - AN INCREASING STELLAR BARYON FRACTION in BRIGHT GALAXIES at HIGH REDSHIFT
AU - Finkelstein, Steven L.
AU - Song, Mimi
AU - Behroozi, Peter
AU - Somerville, Rachel S.
AU - Papovich, Casey
AU - Milosavljević, Miloš
AU - Dekel, Avishai
AU - Narayanan, Desika
AU - Ashby, Matthew L.N.
AU - Cooray, Asantha
AU - Fazio, Giovanni G.
AU - Ferguson, Henry C.
AU - Koekemoer, Anton M.
AU - Salmon, Brett
AU - Willner, S. P.
N1 - Publisher Copyright:
© 2015. The American Astronomical Society. All rights reserved..
PY - 2015/12/1
Y1 - 2015/12/1
N2 - 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 We investigate this apparent non-evolution by examining a sample of 173 bright, MUV < -21 galaxies at z = 4-7, analyzing their stellar populations and host halo masses. Including deep Spitzer/IRAC imaging to constrain the rest-frame optical light, we find that galaxies at z = 4-7 have similar stellar masses of log(M/Mo) = 9.6-9.9 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 for a fixed dust-attenuation curve. Matching the abundances of these bright z = 4-7 galaxies to halo mass functions from the Bolshoi ΛCDM simulation implies that the typical halo masses in galaxies decrease from log(Mh/Mo) = 11.9 at z = 4 to log(Mh/Mo) = 11.4 at z = 7. Thus, although we are studying galaxies at a similar stellar mass across multiple redshifts, these galaxies live in lower mass halos at higher redshift. The stellar baryon fraction in galaxies in units of the cosmic mean Ωb/Ωm rises from 5.1% at z = 4 to 11.7% at z = 7; this evolution is significant at the ∼3σ 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.
AB - 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 We investigate this apparent non-evolution by examining a sample of 173 bright, MUV < -21 galaxies at z = 4-7, analyzing their stellar populations and host halo masses. Including deep Spitzer/IRAC imaging to constrain the rest-frame optical light, we find that galaxies at z = 4-7 have similar stellar masses of log(M/Mo) = 9.6-9.9 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 for a fixed dust-attenuation curve. Matching the abundances of these bright z = 4-7 galaxies to halo mass functions from the Bolshoi ΛCDM simulation implies that the typical halo masses in galaxies decrease from log(Mh/Mo) = 11.9 at z = 4 to log(Mh/Mo) = 11.4 at z = 7. Thus, although we are studying galaxies at a similar stellar mass across multiple redshifts, these galaxies live in lower mass halos at higher redshift. The stellar baryon fraction in galaxies in units of the cosmic mean Ωb/Ωm rises from 5.1% at z = 4 to 11.7% at z = 7; this evolution is significant at the ∼3σ 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.
KW - early universe
KW - galaxies: evolution
KW - galaxies: formation
KW - galaxies: high-redshift
KW - ultraviolet: galaxies
UR - http://www.scopus.com/inward/record.url?scp=84948771316&partnerID=8YFLogxK
U2 - 10.1088/0004-637X/814/2/95
DO - 10.1088/0004-637X/814/2/95
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AN - SCOPUS:84948771316
SN - 0004-637X
VL - 814
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 95
ER -