E. Daddi et al. 2007 ApJ 670 156 doi:10.1086/521818
Multiwavelength Study of Massive Galaxies at z~2. I. Star Formation and Galaxy Growth
FREE ISSUEE. Daddi1, M. Dickinson2, G. Morrison3,4, R. Chary5, A. Cimatti6, D. Elbaz1, D. Frayer5, A. Renzini7, A. Pope8, D. M. Alexander9, F. E. Bauer10, M. Giavalisco11, M. Huynh5, J. Kurk12 and M. Mignoli13
Show affiliationsExamining a sample of massive galaxies at 1.4 < z < 2.5 with KVega < 22 from GOODS, we compare photometry from Spitzer at mid- and far-IR to submillimeter, radio, and rest-frame UV wavelengths, to test the agreement between different tracers of star formation rates (SFRs) and to explore the implications for galaxy assembly. For z ~ 2 galaxies with moderate luminosities (L8 μm < 1011 L
), we find that the SFR can be estimated consistently from the multiwavelength data based on local luminosity correlations. However, 20%-30% of massive galaxies, and nearly all those with L8 μm > 1011 L, show a mid-IR excess that is likely due to the presence of obscured active nuclei, as shown in a companion paper. There is a tight and roughly linear correlation between stellar mass and SFR for 24 μm-detected galaxies. For a given mass, the SFR at z = 2 was larger by a factor of ~4 and ~30 relative to that in star-forming galaxies at z = 1 and 0, respectively. Typical ultraluminous infrared galaxies (ULIRGs) at z = 2 are relatively "transparent" to ultraviolet light, and their activity is long lived (
400 Myr), unlike that in local ULIRGs and high-redshift submillimeter-selected galaxies. ULIRGs are the common mode of star formation in massive galaxies at z = 2, and the high duty cycle suggests that major mergers are not the dominant trigger for this activity. Current galaxy formation models underpredict the normalization of the mass-SFR correlation by about a factor of 4 and the space density of ULIRGs by an order of magnitude but give better agreement for z > 1.4 quiescent galaxies.
- Subject headings
cosmology: observations; galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: starburst
- Dates
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Issue 1 (2007 November 20)
Received 2007 May 19, accepted for publication 2007 July 22
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Multiwavelength Study of Massive Galaxies at z~2. I. Star Formation and Galaxy Growth
E. Daddi et al. 2007 ApJ 670 156
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