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arXiv · 1205.0555

The Characteristic Star Formation Histories of Galaxies at Redshifts z~2-7

Naveen A. Reddy·Max Pettini·Charles C. Steidel·Alice E. Shapley·Dawn K. Erb·David R. Law
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Abstract

A large sample of spectroscopically confirmed galaxies at 1.4 2. The SFRs of z~2-3 galaxies are directly proportional to their stellar masses M*, with unity slope---a result that is confirmed with Spitzer/IRAC stacks of 1179 UV-faint (R>25.5) galaxies---for M*>5e8 Msun and SFRs >2 Msun/yr. We interpret this result in the context of several systematic biases that can affect determinations of the SFR-M* relation. The average specific SFRs at z~2-3 are similar within a factor of two to those measured at z>4, implying an average SFH where SFRs increase with time. A consequence of these rising SFHs is that (a) a substantial fraction of UV-bright z~2-3 galaxies had faint sub-L* progenitors at z>4; and (b) gas masses must increase with time from z=7 to 2, over which time the net cold gas accretion rate---as inferred from the specific SFR and the Kennicutt-Schmidt relation---is ~2-3x larger than the SFR . However, if we evolve to higher redshift the SFHs and masses of the halos that are expected to host L* galaxies at z~2, we find that <10% of the baryons accreted onto typical halos at z>4 actually contribute to star formation at those epochs. These results highlight the relative inefficiency of star formation even at early cosmic times when galaxies were first assembling. [Abridged]

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Naveen A. Reddy, Max Pettini, Charles C. Steidel, Alice E. Shapley, Dawn K. Erb, David R. Law. 2012-05-02. The Characteristic Star Formation Histories of Galaxies at Redshifts z~2-7. https://doi.org/10.1088/0004-637x%2F754%2F1%2F25

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