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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 421728.0, MPI für Astronomie / Publikationen_mpia
Star formation rates in Lyman break galaxies: radio stacking of LBGs in the COSMOS field and the Sub-μJy radio source population
Authors:Carilli, C. L.; Lee, Nicholas; Capak, P.; Schinnerer, E.; Lee, K. S.; McCraken, H.; Yun, M. S.; Scoville, N.; Smolcic, V.; Giavalisco, M.; Datta, A.; Taniguchi, Y.; Urry, C. Megan
Date of Publication (YYYY-MM-DD):2008
Title of Journal:The Astrophysical Journal
Start Page:883
End Page:888
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:We present an analysis of the radio properties of large samples of Lyman break galaxies (LBGs) at z~3, 4, and 5 from the COSMOS field. The median stacking analysis yields a statistical detection of the z~3 LBGs (U-band dropouts), with a 1.4 GHz flux density of 0.90+/-0.21 muJy. The stacked emission is unresolved, with a size <1, or a physical size <8 kpc. The total star formation rate implied by this radio luminosity is 31+/-7 Msolar yr-1, based on the radio-FIR correlation in low-redshift star-forming galaxies. The star formation rate derived from a similar analysis of the UV luminosities is 17 Msolar yr-1, without any correction for UV dust attenuation. The simplest conclusion is that the dust attenuation factor is 1.8 at UV wavelengths. However, this factor is considerably smaller than the standard attenuation factor of ~5, normally assumed for LBGs. We discuss potential reasons for this discrepancy, including the possibility that the dust attenuation factor at z>=3 is smaller than at lower redshifts. Conversely, the radio luminosity for a given star formation rate may be systematically lower at very high redshift. Two possible causes for a suppressed radio luminosity are (1) increased inverse Compton cooling of the relativistic electron population due to scattering off the increasing CMB at high redshift or (2) cosmic-ray diffusion from systematically smaller galaxies. The radio detections of individual sources are consistent with a radio-loud AGN fraction of 0.3%. One source is identified as a very dusty, extreme starburst galaxy (a ``submillimeter galaxy''). Based on observations in the COSMOS Legacy Survey including those taken on the HST, Keck, NRAO-VLA, Subaru, KPNO 4 m, CTIO 4 m, and CFHT 3.6 m. The Very Large Array of the National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
Free Keywords:Galaxies: Evolution; Galaxies: Formation; Surveys
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL: [ID No:1]
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