The quest for obscured AGN at cosmological distances: Infrared power-law galaxies

A. Alonso-Herrero, J. L. Donley, G. H. Rieke, J. R. Rigby, P. G. Pérez-González

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We summarize multiwavelength properties of a sample of galaxies in the CDF-N and CDF-S whose spectral energy distributions (SEDs) exhibit the characteristic power-law behavior expected for AGN in the Spitzer/IRAC 3.6-8 μm bands. AGN selected this way tend to comprise the majority of high x-ray luminosity AGN, whereas AGN selected via other IRAC color-color criteria might contain more starformation dominated galaxies. Approximately half of these IR power-law galaxies in the CDF-S are detected in deep (1 Ms) Chandra x-ray imaging, although in the CDF-N (2 Ms) about 77% are detected at the 3 σlevel. The SEDs and x-ray upper limits of the sources not detected in x-rays are consistent with those of obscured AGN, and are significantly different from those of massive star-forming galaxies. About 40% of IR power-law galaxies detected in x-rays have SEDs resembling that of an optical QSO and morphologies dominated by bright point source emission. The remaining 60% have SEDs whose UV and optical continuum are much steeper (obscured) and more extended morphologies than those detected in x-rays. Most of the IR power-law galaxies not detected in x-rays have IR (8?1000 μm) above 1012 L, and x-ray (upper limits) to mid-IR ratios similar to those of local warm (i.e. hosting an AGN) ULIRGs. The SED shapes of power-law galaxies are consistent with the obscured fraction (4:1) as derived from the x-ray column densities, if we assume that all the sources not detected in x-rays are heavily absorbed. IR power-law galaxies may account for between 20% and 50% of the predicted number density of mid-IR detected obscured AGN. The remaining obscured AGN probably have rest-frame SEDs dominated by stellar emission.

Original languageEnglish (US)
Title of host publicationHighlights of Spanish Astrophysics IV - Proceedings of the 7th Scientific Meeting of the Spanish Astronomical Society, SEA 2006
Pages143-155
Number of pages13
DOIs
StatePublished - Dec 1 2007
Event7th Scientific Meeting of the Spanish Astronomical Society, SEA 2006 - Barcelona, Spain
Duration: Sep 12 2006Sep 15 2006

Publication series

NameHighlights of Spanish Astrophysics IV - Proceedings of the 7th Scientific Meeting of the Spanish Astronomical Society, SEA 2006

Other

Other7th Scientific Meeting of the Spanish Astronomical Society, SEA 2006
CountrySpain
CityBarcelona
Period9/12/069/15/06

ASJC Scopus subject areas

  • Astronomy and Astrophysics

Fingerprint Dive into the research topics of 'The quest for obscured AGN at cosmological distances: Infrared power-law galaxies'. Together they form a unique fingerprint.

Cite this