INFRARED AND HARD X-RAY DIAGNOSTICS OF ACTIVE GALACTIC NUCLEUS IDENTIFICATION FROM THE SWIFT /BAT AND AKARI ALL-SKY SURVEYS

• Published in: The Astrophysical journal Vol. 753; no. 2; pp. 104 - 16
• Main Authors: Matsuta, K., Gandhi, P., Dotani, T., Nakagawa, T., Isobe, N., Ueda, Y., Ichikawa, K., Terashima, Y., Oyabu, S., Yamamura, I., Stawarz, Ł.
• Format: Journal Article
• Language: English
• Published: Bristol IOP 10.07.2012
• Subjects: Active galactic nuclei; ASTRONOMY; ASTROPHYSICS; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Classification; COLOR; COMPTON EFFECT; Correlation; CORRELATIONS; Diagnostic systems; DIAGRAMS; Earth, ocean, space; Exact sciences and technology; GALAXY NUCLEI; HARD X RADIATION; Indicators; Infrared; INFRARED SPECTRA; KEV RANGE; LUMINOSITY; PHOTOMETRY; RADIO GALAXIES; RED SHIFT; SEYFERT GALAXIES; X-RAY GALAXIES; X-RAY SPECTRA; X-rays; Red shift; Hard x radiation; infrared: galaxies; X-ray galaxies; Radio galaxies; High density; Starburst galaxies; X-rays: galaxies; Color; Cosmic x-ray sources; Luminosity; Column density; Active galaxies; Correlation analysis; Strong correlation; galaxies: active; Active galaxy nuclei; Classification; Galaxy nuclei; Cosmic radio sources; Infrared galaxies; Sky surveys; X ray emission; Seyfert 1 galaxies
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/753/2/104

We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10 keV) properties for local active galactic nuclei (AGNs). The Swift Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X-ray-detected AGNs. Cross-correlating the 22 month hard X-ray survey with the AKARI all-sky survey, we studied 158 AGNs detected by the AKARI instruments. We find a strong correlation for most AGNs between the infrared (9, 18, and 90 mu m) and hard X-ray (14-195 keV) luminosities, and quantify the correlation for various subsamples of AGNs. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1 galaxies, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick (CT) sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity versus infrared color diagram, in which type 1 radio-loud AGNs are well isolated from the others in the sample. The other uses the X-ray versus infrared color as a useful redshift-independent indicator for identifying CT AGNs. Importantly, CT AGNs and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR.