GOODS-Herschel Measurements of the Dust Attenuation of Typical Star-forming Galaxies at High Redshift: Observations of Ultraviolet-selected Galaxies at z ~ 2

Abstract

We take advantage of the sensitivity and resolution of the Herschel Space Observatory at 100 and 160 μm to directly image the thermal dust emission and investigate the infrared luminosities (L_IR) and dust obscuration of typical star-forming (L*) galaxies at high redshift. Our sample consists of 146 UV-selected galaxies with spectroscopic redshifts 1.5 ≤ z_spec < 2.6 in the GOODS-North field. Supplemented with deep Very Large Array and Spitzer imaging, we construct median stacks at the positions of these galaxies at 24, 100, and 160 μm, and 1.4 GHz. The comparison between these stacked fluxes and a variety of dust templates and calibrations implies that typical star-forming galaxies with UV luminosities L_UV ≳ 10^(10) L_☉ at z ~ 2 are luminous infrared galaxies with a median L_IR = (2.2 ± 0.3) × 10^(11) L_☉. Their median ratio of L IR to rest-frame 8 μm luminosity (L_8) is L_(IR)/L_8 = 8.9 ± 1.3 and is ≈80% larger than that found for most star-forming galaxies at z ≲ 2. This apparent redshift evolution in the L_(IR)/L_8 ratio may be tied to the trend of larger infrared luminosity surface density for z ≳ 2 galaxies relative to those at lower redshift. Typical galaxies at 1.5 ≤ z < 2.6 have a median dust obscuration L_(IR)/L_(UV) = 7.1 ± 1.1, which corresponds to a dust correction factor, required to recover the bolometric star formation rate (SFR) from the unobscured UV SFR, of 5.2 ± 0.6. This result is similar to that inferred from previous investigations of the UV, Hα, 24 μm, radio, and X-ray properties of the same galaxies studied here. Stacking in bins of UV slope (β) implies that L* galaxies with redder spectral slopes are also dustier and that the correlation between β and dustiness is similar to that found for local starburst galaxies. Hence, the rest-frame ≃30 and 50 μm fluxes validate on average the use of the local UV attenuation curve to recover the dust attenuation of typical star-forming galaxies at high redshift. In the simplest interpretation, the agreement between the local and high-redshift UV attenuation curves suggests a similarity in the dust production and stellar and dust geometries of starburst galaxies over the last 10 billion years.

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