[Ultra] Luminous Infrared Galaxies selected at 90 $\mu$m in the AKARI
  deep field: a study of AGN types contributing to their infrared emission
  The aim of this work is to characterize physical properties of Ultra Luminous
Infrared Galaxies (ULIRGs) and Luminous Infrared Galaxies (LIRGs) detected in
the far-infrared (FIR) 90um band in the AKARI Deep Field-South (ADF-S) survey.
In particular, we want to estimate the AGN contribution to the [U]LIRGs'
infrared emission and which types of AGNs are related to their activity. We
examined 69 galaxies at z>0.05 detected at 90um by the AKARI satellite in the
ADF-S, with optical counterparts and spectral coverage from the ultraviolet to
the FIR. We used two independent spectral energy distribution fitting codes:
one fitting the SED from FIR to FUV (CIGALE) and gray-body + power spectrum fit
for the infrared part of the spectra (CMCIRSED) in order to identify a
subsample of [U]LIRGs, and to estimate their properties. Based on the CIGALE
SED fitting, we have found that [U]LIRGs selected at the 90um AKARI band
compose ~56% of our sample (we found 17 ULIRGs and 22 LIRGs, spanning over the
redshift range 0.06<z<1.23). Their physical parameters, such as stellar mass,
star formation rate (SFR), and specific SFR are consistent with the ones found
for other samples selected at IR wavelengths. We have detected a significant
AGN contribution to the MIR luminosity for 63% of LIRGs and ULIRGs. Our LIRGs
contain Type 1, Type 2, and intermediate types of AGN, whereas for ULIRGs, a
majority (more than 50%) of AGN emission originates from Type 2 AGNs. The
temperature--luminosity and temperature--mass relations for the dust component
of ADF--S LIRGs and ULIRGs indicate that these relations are shaped by the dust
mass and not by the increased dust heating. We conclude that LIRGs contain Type
1, Type 2, and intermediate types of AGNs, with an AGN contribution to the MIR
emission at the median level of 13+/-3%, whereas the majority of ULIRGs contain
Type 2 AGNs, with a median AGN fraction equal to 19+/-8%.
