Star Formation Rate and Extinction in Faint z~4 Lyman-Break Galaxies

Abstract

We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z~4 Lyman-break galaxies (LBGs). LBGs are key tracers of the high-redshift star formation history and important sources of UV photons that ionized the intergalactic medium in the early universe. In order to better constrain the extinction and intrinsic star formation rate (SFR) of high-redshift LBGs, we combine the latest ultradeep Karl G. Jansky Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advance Camera for Surveys (ACS) optical images in the Great Observatories Origins Deep Survey-North. We select a large sample of 1771 z~4 LBGs from the ACS catalogue using $\bband$-dropout color criteria. Our LBG samples have $\iband$~25-28 (AB), ~0-3 magnitudes fainter than M*_UV at z~4. In our stacked radio images, we find the LBGs to be point-like under our 2" angular resolution. We measure their mean 1.5 GHz flux by stacking the measurements on the individual objects. We achieve a statistical detection of $S_{1.5GHz}$=0.210+-0.075 uJy at ~3 sigma, first time on such a faint LBG population at z~4. The measurement takes into account the effects of source size and blending of multiple objects. The detection is visually confirmed by stacking the radio images of the LBGs, and the uncertainty is quantified with Monte Carlo simulations on the radio image. The stacked radio flux corresponds to an intrinsic SFR of 16.0+-5.7 M/yr, which is 2.8X the SFR derived from the rest-frame UV continuum luminosity. This factor of 2.8 is in excellent agreement with the extinction correction derived from the observed UV continuum spectral slope, using the local calibration of meurer99. This result supports the use of the local calibration on high-redshift LBGs for deriving the extinction correction and SFR, and also disfavors a steep reddening curve such as that of the Small Magellanic Cloud.

9 pages, 6 figures, 1 table. Accepted to ApJ. Comments are welcome

References in corpus (11)

• The Hubble Ultra Deep Field
• UV Luminosity Functions at z~4, 5, and 6 from the HUDF and other Deep HST ACS Fields: Evolution and Star Formation History
• Subaru Deep Survey V. A Census of Lyman Break Galaxies at z=4 and 5 in the Subaru Deep Fields: Photometric Properties
• Dust Formation and Survival in Supernova Ejecta
• Spectroscopic Confirmation Of An Extreme Starburst At Redshift 4.547
• The VLA 1.4GHz Survey of the Extended Chandra Deep Field South: First Data Release
• An AzTEC 1.1 mm Survey of the GOODS-N Field I: Maps, Catalogue, and Source Statistics
• Lyman-break galaxies at z~5 -I. First significant stellar mass assembly in galaxies that are not simply z~3 LBGs at higher redshift
• Constraints on the star-formation rate of z~3 LBGs with measured metallicity in the CANDELS GOODS-South field
• Star formation rates in Lyman break galaxies: radio stacking of LBGs in the COSMOS field and the sub-$\mu$Jy radio source population
• Ultradeep Near-Infrared Observations of GOODS 850-5

Cited by in corpus (6)

• Are Dusty Galaxies Blue? Insights on UV Attenuation from Dust-Selected Galaxies
• Are high redshift Galaxies hot? - Temperature of z > 5 Galaxies and Implications on their Dust Properties
• The IRX-Beta Dust Attenuation Relation in Cosmological Galaxy Formation Simulations
• A spatially resolved study of cold dust, molecular gas, HII regions, and stars in the $z=2.12$ submillimeter galaxy ALESS67.1
• Dissecting the IRX - $\beta$ dust attenuation relation: exploring the physical origin of observed variations in galaxies
• SXDF-ALMA 2-arcmin^2 Deep Survey: Stacking of Rest-Frame Near-Infrared Selected Objects