Abstract
We present the 18 ㎛ luminosity function (LF) of galaxies at 0.006 < z < 0.8 (the average redshift is~0.04) using the AKARI mid-infrared All-Sky Survey catalogue. We have selected 243 galaxies at 18 ㎛ from the Sloan Digital Sky Survey (SDSS) spectroscopic region. These galaxies then have been classified into five types; Seyfert 1 galaxies (Sy1, including quasars), Seyfert 2 galaxies (Sy2), low ionization narrow emission line galaxies (LINER), galaxies that are likely to contain both star formation and Active Galactic Nuclei (AGN) activities (composites), and star forming galaxies (SF) using optical emission lines such as the line width of Hα or the emission line ratios of [OIII]/Hβ and [NII]/Hα. As a result of constructing the LF of Sy1 and Sy2, we found the following results; (i) the number density ratio of Sy2 to Sy1 is 1.64 ± 0.37, larger than the results obtained from optical LF and (ii) the fraction of Sy2 in the entire AGN population may decrease with 18 ㎛ luminosity. These results suggest that most of the AGNs in the local universe are obscured by dust and the torus structure probably depends on the mid-infrared luminosity.
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