SURVEY OF DUSTY ACTIVE GALACTIC NUCLEI BASED ON THE MID-INFRARED ALL-SKY SURVEY CATALOG

Abstract

Many observations have found evidence of the presence of a large number of heavily obscured Active Galactic Nuclei (AGNs). However, the nature of this population is only poorly understood because heavy obscuration by dust prevents one from finding them at optical wavelengths. Midinfrared AGN searches can overcome this obstacle by penetrating through dust and by detecting direct emission from the dust torus. Thus, we can identify most of the AGN population, including type-2 and buried AGNs. Using the AKARI mid-infrared all-sky survey, we performed an AGN search in the nearby universe. Utilizing the 2MASS photometry, we selected mid-infrared-excess sources and carried out near-infrared spectroscopic observations in the AKARI Phase 3. During these follow-up observations, we have found three galaxies that show strong near-infrared red continuum from hot dust with a temperature of about 500 K, but do not show any AGN features in other wavelengths. The most suitable explanation of near-infrared continuum is the presence of central AGNs. Therefore, we conclude that they are AGNs obscured by dust. We performed X-ray observations of the two galaxies with SUZAKU. No detections in the 0.4-10 keV suggest that the column density may be much higher than N H = 10 23:5 cm -2 . Comparing the masses of the host galaxies with those of the SDSS AGNs, we find that the host galaxies of the dusty AGNs discovered with AKARI are less massive populations than those of optically selected AGNs.