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.

Accepted 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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