Are Dusty Galaxies Blue? Insights on UV Attenuation from Dust-Selected Galaxies

C. M Casey; N. Z Scoville; D. B Sanders; N Lee; A Cooray; S. L Finkelstein; P Capak; A Conley; G De Zotti; D Farrah; H Fu; E. Le Floc'h; O Ilbert; R. J Ivison; T. T Takeuchi

doi:10.1088/0004-637X/796/2/95

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Are Dusty Galaxies Blue? Insights on UV Attenuation from Dust-Selected Galaxies

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Are Dusty Galaxies Blue? Insights on UV Attenuation from Dust-Selected Galaxies

C. M Casey, N. Z Scoville, D. B Sanders, N Lee, A Cooray, S. L Finkelstein, P Capak, A Conley, G De Zotti, D Farrah, …

The Astrophysical journal, Vol.796(2), pp.1-15

10/02/2014

DOI: 10.1088/0004-637X/796/2/95

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Abstract

Galaxies' rest-frame ultraviolet (UV) properties are often used to directly infer the degree to which dust obscuration affects the measurement of star formation rates. While much recent work has focused on calibrating dust attenuation in galaxies selected at rest-frame ultraviolet wavelengths, locally and at high-$z$, here we investigate attenuation in dusty, star-forming galaxies (DSFGs) selected at far-infrared wavelengths. By combining multiwavelength coverage across 0.15--500\,$\mu$m in the COSMOS field, in particular making use of {\it Herschel} imaging, and a rich dataset on local galaxies, we find a empirical variation in the relationship between rest-frame UV slope ($\beta$) and ratio of infrared-to-ultraviolet emission ($L_{\rm IR}/L_{\rm UV}\equiv\,IRX$) as a function of infrared luminosity, or total star formation rate, SFR. Both locally and at high-$z$, galaxies above SFR$\gt$50\,M$_\odot$\,yr$^{-1}$ deviate from the nominal $IRX-\beta$ relation towards bluer colors by a factor proportional to their increasing IR luminosity. We also estimate contamination rates of DSFGs on high-$z$ dropout searches of $\ll1$\%\ at $z\lt4-10$, providing independent verification that contamination from very dusty foreground galaxies is low in LBG searches. Overall, our results are consistent with the physical interpretation that DSFGs, e.g. galaxies with $>50$\,M$_\odot$\,yr$^{-1}$, are dominated at all epochs by short-lived, extreme burst events, producing many young O and B stars that are primarily, yet not entirely, enshrouded in thick dust cocoons. The blue rest-frame UV slopes of DSFGs are inconsistent with the suggestion that most DSFGs at $z\sim2$ exhibit steady-state star formation in secular disks.

Details

Title: Subtitle: Are Dusty Galaxies Blue? Insights on UV Attenuation from Dust-Selected Galaxies
Creators: C. M Casey - University of California, Irvine
N. Z Scoville - California Institute of Technology
D. B Sanders - IFA Hawaii
N Lee - IFA Hawaii
A Cooray - University of California, Irvine
S. L Finkelstein - University of Texas at Austin
P Capak - California Institute of Technology
A Conley - University of Colorado Boulder
G De Zotti - Scuola Internazionale Superiore di Studi Avanzati
D Farrah - Virginia Tech
H Fu - University of Iowa
E. Le Floc'h - CEA Paris-Saclay
O Ilbert - Aix Marseille
R. J Ivison - University of Edinburgh
T. T Takeuchi - Nagoya University
Resource Type: Journal article
Publication Details: The Astrophysical journal, Vol.796(2), pp.1-15
DOI: 10.1088/0004-637X/796/2/95
ISSN: 0004-637X
eISSN: 1538-4357
Publisher: Institute of Physics (IOP)
Language: English
Date published: 10/02/2014
Academic Unit: Physics and Astronomy
Record Identifier: 9984199790702771

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