THE ROLE OF STAR FORMATION AND AN AGN IN DUST HEATING OF z = 0.3–2.8 GALAXIES. I. EVOLUTION WITH REDSHIFT AND LUMINOSITY
- Department of Astronomy, University of Massachusetts, Amherst, MA 01002 (United States)
- Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)
- Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)
- Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
- Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile)
- Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States)
We characterize infrared spectral energy distributions of 343 (ultra)luminous infrared galaxies from z = 0.3–2.8. We diagnose the presence of an active galactic nucleus (AGN) by decomposing individual Spitzer mid-IR spectroscopy into emission from star formation and an AGN-powered continuum; we classify sources as star-forming galaxies (SFGs), AGNs, or composites. Composites comprise 30% of our sample and are prevalent at faint and bright S{sub 24}, making them an important source of IR AGN emission. We combine spectroscopy with multiwavelength photometry, including Herschel imaging, to create three libraries of publicly available templates (2–1000 μm). We fit the far-IR emission using a two-temperature modified blackbody to measure cold and warm dust temperatures (T{sub c} and T{sub w}). We find that T{sub c} does not depend on mid-IR classification, while T{sub w} shows a notable increase as the AGN grows more luminous. We measure a quadratic relationship between mid-IR AGN emission and total AGN contribution to L{sub IR}. AGNs, composites, and SFGs separate in S{sub 8}/S{sub 3.6} and S{sub 250}/S{sub 24}, providing a useful diagnostic for estimating relative amounts of these sources. We estimate that >40% of IR-selected samples host an AGN, even at faint selection thresholds (S{sub 24} > 100 μJy). Our decomposition technique and color diagnostics are relevant given upcoming observations with the James Webb Space Telescope.
- OSTI ID:
- 22521913
- Journal Information:
- Astrophysical Journal, Vol. 814, 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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