Noeske, K. G. and Faber, S. M. and Weiner, B. J. and Koo, D. C. and Primack, J. R. and Dekel, A. and Papovich, C. and Conselice, C. J. and Le Floc'h, E. and Rieke, G. H. and Coil, A. L. and Lotz, J. M. and Somerville, R. S. and Bundy, K. (2007) Star Formation in AEGIS Field Galaxies since z = 1.1: Staged Galaxy Formation and a Model of Mass-dependent Gas Exhaustion. Astrophysical Journal Letters, 660 (1). L47-L50. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:NOEapjl07b
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We analyze star formation (SF) as a function of stellar mass (M☉) and redshift z in the All-Wavelength Extended Groth Strip International Survey, for star-forming field galaxies with M* ≳ 10^10 M☉ out to z = 1.1. The data indicate that the high specific SF rates (SFRs) of many less massive galaxies do not represent late, irregular or recurrent, starbursts in evolved galaxies. They rather seem to reflect the onset (initial burst) of the dominant SF episode of galaxies, after which SF gradually declines on gigayear timescales to z = 0 and forms the bulk of a galaxy’s M*. With decreasing mass, this onset of major SF shifts to decreasing z for an increasing fraction of galaxies (staged galaxy formation). This process may be an important component of the “downsizing” phenomenon. We find that the predominantly gradual decline of SFRs described by Noeske et al. can be reproduced by exponential SF histories (τ models), if less massive galaxies have systematically longer e-folding times τ, and a later onset of SF (zf). Our model can provide a first parameterization of SFR as a function of M* and z, and quantify mass dependences of τ and z, from direct observations of M* and SFRs up to z > 1. The observed evolution of SF in galaxies can plausibly reflect the dominance of gradual gas exhaustion. The data are also consistent with the history of cosmological accretion onto dark matter halos.
|Additional Information:||© 2007. The American Astronomical Society. Received 2006 June 4; accepted 2007 March 2; published 2007 April 3. See the survey summary Letter (Davis et al. 2007) for full acknowledgments. This work is based on observations with the W.M. Keck Telescope, the Hubble Space Telescope, the Galaxy Evolution Explorer, the Canada-France-Hawaii Telescope, and the Palomar Observatory, and was supported by NASA and NSF grants. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through contract numbers 1256790, 960785, and 1255094 issued by JPL/Caltech. K.G.N. acknowledges support from the Aspen Center for Physics. We wish to thank the referee for helpful comments. [A.L.C. was a] Hubble Fellow. [J.M.L. was a] Leo Goldberg Fellow, National Optical Astronomy Observatory.|
|Subject Keywords:||galactic evolution; —galaxy formation; high-redshift galaxies; starburst|
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|Deposited By:||Archive Administrator|
|Deposited On:||12 Aug 2008 19:23|
|Last Modified:||26 Dec 2012 10:13|
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