The quest for obscured AGN at cosmological distances: Infrared Power-Law Galaxies

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dc.creatorAlonso-Herrero, Almudena
dc.creatorDonley, Jennifer L.
dc.creatorRieke, George H.
dc.creatorRigby, Jane R.
dc.creatorPerez-Gonzalez, Pablo G.
dc.date2006-12-04
dc.date.accessioned2026-07-07T07:31:02Z
dc.date.available2026-07-07T07:31:02Z
dc.descriptionWe 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 3.6-8micron 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 star-formation dominated galaxies. Approximately half of these IR power-law galaxies in the CDF-S are detected in deep (1Ms) Chandra X-ray imaging, although in the CDF-N (2Ms) about 77% are detected at the 3sigma level. 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 (8-1000micron above 10^12Lsun, and X-ray (upper limits) to mid-IR ratios similar to those of local warm (ie, 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.
dc.descriptionInvited talk at the Meeting of Spanish Astronomical Society to be publised in " Highlights of Spanish Astrophysics IV " Proceedings of the VII Scientific Meeting of the Spanish Astronomical Society (SEA) held in Barcelona, September 12-15, 2006, Springer. Paper with high resolution images can be found at http://damir.iem.csic.es/extragalactic/publications/publications.html
dc.identifierhttps://arxiv.org/abs/astro-ph/0612068
dc.identifierhttp://arxiv.org/abs/astro-ph/0612068
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/118613
dc.subjectAstrophysics
dc.titleThe quest for obscured AGN at cosmological distances: Infrared Power-Law Galaxies
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