paper

The role of star-formation and AGN in dust heating of z = 0.3-2.8 galaxies - I. Evolution with redshift and luminosity

arXiv:1510.02806 · doi:10.1088/0004-637X/814/1/9

Abstract

We characterize infrared spectral energy distributions of 343 (Ultra) Luminous Infrared Galaxies from . We diagnose the presence of an 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), AGN, or composites. Composites comprise 30% of our sample and are prevalent at faint and bright , 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 m). We fit the far-IR emission using a two temperature modified blackbody to measure cold and warm dust temperatures ( and ). We find that does not depend on mid-IR classification, while 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 . AGN, composites, and SFGs separate in and , 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 (>100 Jy). Our decomposition technique and color diagnostics are relevant given upcoming observations with the James Webb Space Telescope.

arXiv commentAccepted for publication in ApJ. Publicly available templates are at http://www.astro.umass.edu/~pope/Kirkpatrick2015. Due to size limitations, Appendix B could not be included in the arXiv submission

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