EVIDENCE FOR A WIDE RANGE OF ULTRAVIOLET OBSCURATION IN z {approx} 2 DUSTY GALAXIES FROM THE GOODS-HERSCHEL SURVEY
- Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States)
- National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)
- Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)
- Max Planck Institut fuer Extraterrestrische Physik, Postfach 1312, D-85741 Garching (Germany)
- Laboratoire AIM Paris-Saclay, CEA/DSM/Irfu-CNRS-Universite Paris Diderot, CEA-Saclay, pt courrier 131, F-91191 Gif-sur-Yvette (France)
- Herschel Science Center, European Space Astronomy Center, Villanueva de la Canada, E-28691 Madrid (Spain)
- Laboratoire d'Astrophysique de Marseille, OAMP, Universite Aix-marseille, CNRS, 38 rue Frederic Joliot-Curie, F-13388 Marseille Cedex 13 (France)
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
- Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, GR-71003 Heraklion (Greece)
- Institut fuer Astronomie, Universitaet Wien, Tuerkenschanzstrasse 17, A-1180 Vienna (Austria)
- Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 106, Taiwan (China)
- Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom)
- Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)
Dusty galaxies at z {approx} 2 span a wide range of relative brightness between rest-frame mid-infrared (8 {mu}m) and ultraviolet wavelengths. We attempt to determine the physical mechanism responsible for this diversity. Dust-obscured galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios {approx}> 1000, might be abnormally bright in the mid-IR, perhaps due to prominent emission from active galactic nuclei and/or polycyclic aromatic hydrocarbons, or abnormally faint in the UV. We use far-infrared data from the GOODS-Herschel survey to show that most DOGs with 10{sup 12} L {sub Sun} {approx}< L {sub IR} {approx}< 10{sup 13} L {sub Sun} are not abnormally bright in the mid-IR when compared to other dusty galaxies with similar IR (8-1000 {mu}m) luminosities. We observe a relation between the median IR to UV luminosity ratios and the median UV continuum power-law indices for these galaxies, and we find that only 24% have specific star formation rates that indicate the dominance of compact star-forming regions. This circumstantial evidence supports the idea that the UV- and IR-emitting regions in these galaxies are spatially coincident, which implies a connection between the abnormal UV faintness of DOGs and dust obscuration. We conclude that the range in rest-frame mid-IR to UV flux density ratios spanned by dusty galaxies at z {approx} 2 is due to differing amounts of UV obscuration. Of galaxies with these IR luminosities, DOGs are the most obscured. We attribute differences in UV obscuration to either (1) differences in the degree of alignment between the spatial distributions of dust and massive stars or (2) differences in the total dust content.
- OSTI ID:
- 22086471
- Journal Information:
- Astrophysical Journal, Vol. 759, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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