Luminosity functions of local infrared galaxies with AKARI: implications for the cosmic star formation history and AGN evolution

Infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and active galactic nuclei (AGN) evolution, since their most intense stages are often obscured by dust. However, local IR luminosity function estimates today are still based on the IRAS survey in the 1980s, with wavelength coverage only up to 100 mu m. The AKARI IR space telescope performed an all-sky survey in six IR bands (9, 18, 65, 90, 140 and 160 mu m) with 3-10 times better sensitivity, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can much more precisely measure the total infrared luminosity (L-TIR) of individual galaxies, and thus, the total infrared luminosity density in the local Universe. By fitting modern IR spectral energy distribution (SED) models, we have remeasured L-TIR of the IRAS Revised Bright Galaxy Sample, which is a complete sample of local galaxies with S-60 mu m > 5.24 Jy. We present mid-IR monochromatic luminosity (nu L-nu) to L-TIR correlations for Spitzer 8 mu m, AKARI 9 mu m, IRAS 12 mu m, WISE 12 mu m, ISO 15 mu m, AKARI 18 mu m, WISE 22 mu m and Spitzer 24 mu m filters. These measures of L-MIR are well correlated with L-TIR, with scatter in the range 13-44 per cent. The best-fitting L-MIR-to-L-TIR conversions provide us with estimates of L-TIR using only a single MIR band, in which several deep all-sky surveys are becoming available such as AKARI MIR and WISE. Although we have found some overestimates of L-TIR by IRAS due to contaminating cirrus/sources, the resulting AKARI IR luminosity function (LF) agrees well with that from IRAS. We integrate the LF weighted by L-TIR to obtain a cosmic IR luminosity density of (TIR) = (8.5+1.5(-2.3)) x 107 L-circle dot Mpc-3, of which 7 +/- 1 per cent is produced by luminous infrared galaxies (LIRGs) (L-TIR > 1011 L-circle dot), and only 0.4 +/- 0.1 per cent is from ultraluminous infrared galaxies (ULIRGs) (L-TIR > 1012 L-circle dot) in the local Universe, in stark contrast to high-redshift results. We separate the contributions from AGN and star-forming galaxies (SFGs). The SFG IR LF shows a steep decline at the bright end. Combined with high-redshift results from the AKARI NEP deep survey, these data show a strong evolution of SFTIR proportional to (1 + z)4.0 +/- 0.5 and AGN(TIR) proportional to (1 + z)4.4 +/- 0.4. For AGN(TIR), the ULIRG contribution exceeds that from LIRGs already by z similar to 1. A rapid evolution in both AGN(TIR) and SFG(TIR) suggests the correlation between star formation and black hole accretion rate continues up to higher redshifts. We compare the evolution of AGN(TIR) to that of X-ray luminosity density. The AGN(TIR)/(X-ray) AGN ratio shows a possible increase at z > 1, suggesting an increase of obscured AGN at z > 1.