Erb, Dawn K. and Steidel, Charles C. and Shapley, Alice E. and Pettini, Max and Reddy, Naveen A. and Adelberger, Kurt L. (2006) Hα Observations of a Large Sample of Galaxies at z ~ 2: Implications for Star Formation in High-Redshift Galaxies. Astrophysical Journal, 647 (1). pp. 128-139. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20110225-160800612
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Using Hα spectra of 114 rest-frame UV-selected galaxies at z ~ 2, we compare inferred star formation rates (SFRs) with those determined from the UV continuum luminosity. After correcting for extinction using standard techniques based on the UV continuum slope, we find excellent agreement between the indicators, with <SFR_(Hα)> = 31 M_☉ yr^(-1) and <SFR_UV> = 29 M_☉ yr^(-1). The agreement between the indicators suggests that the UV luminosity is attenuated by a typical factor of ~4.5 (ranging from no attenuation to a factor of ~100 for the most obscured object in the sample), in good agreement with estimates of obscuration from X-ray, radio, and mid-IR data. The Hα luminosity is attenuated by a factor of ~1.7 on average, and the maximum Hα attenuation is a factor of ~5. In agreement with X-ray and mid-IR studies, we find that the SFR increases with increasing stellar mass and at brighter K magnitudes to <SFRHα> ~ 60 M_☉ yr^(-1) for galaxies with K_s < 20; the correlation between K magnitude and SFR is much stronger than the correlation between stellar mass and SFR. All galaxies in the sample have SFRs per unit area Σ_(SFR) in the range observed in local starbursts. We compare the instantaneous SFRs and the past average SFRs as inferred from the ages and stellar masses, finding that for most of the sample, the current SFR is an adequate representation of the past average. There is some evidence that the most massive galaxies (M_* > 10^(11) M_☉) have had higher SFRs in the past.
|Additional Information:||© 2006 American Astronomical Society. Received 2006 February 14; accepted 2006 April 18. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. We thank Andrew Blain, Jonathan Bird, David Kaplan, and Shri Kulkarni for obtaining near-IR images of some of our targets, and the staffs of the Keck and Palomar observatories for their assistance with the observations. We also thank the anonymous referee for a useful report. C. C. S., D. K. E., and N. A. R. have been supported by grant AST 03-07263 from the US National Science Foundation and by the David and Lucile Packard Foundation. A. E. S. acknowledges support from the Miller Institute for Basic Research in Science, and K. L. A. from the Carnegie Institution of Washington. Finally, we wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, most of the observations presented herein would not have been possible.|
|Subject Keywords:||galaxies: evolution; galaxies: high-redshift; stars: formation|
|Official Citation:||Dawn K. Erb et al. 2006 ApJ 647 128 doi: 10.1086/505341|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||28 Feb 2011 21:25|
|Last Modified:||26 Dec 2012 12:58|
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