Far infrared properties of OH megamaser host galaxies

Abstract

The hosts of OH megamaser (OHM) are luminous infrared galaxies (LIRGs), in fact 1/3 of them are ultra-luminous infrared galaxies (ULIRGs), which imply that OHM phenomena should be related to the infrared radiation field. In this paper, we investigate the far infrared (FIR) properties of OHM host galaxies, through detailed infrared data covering broad bands. All known OHM sources and one control sample of (U)LIRGs without maser detections (non-OHM sources) are cross-identified with AKARI and Herschel photometric catalogs. Comparative analysis on the spectral energy distribution (SED) with broad coverage from J to 350 $\mu$m (taken from 2MASS, WISE, Spitzer, and AKARI and Herschel archive data) shows that the OHM sources tend to have higher FIR luminosities than those of the non-OHM sources, which are more pronounced in the SED range covered by the AKARI. These are consistent with our statistical results of the FIR luminosities distribution of both the samples, which show that the OHM sources tend to have higher FIR luminosities, especially, at short FIR wavelength (i.e., the 65 and 90 $\mu$m). However, the non-OHM sources tend to have much stronger emission than those of OHM sources at both the near infrared (NIR) and middle infrared (MIR) bands. The statistic analysis of the color–color properties at MIR and FIR bands shows that the OHM sources have much cooler MIR and warmer FIR colors than non-OHM sources. These clues could help us to choose OHM candidates for future OHM surveys with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), where the OHM detection rate may exceed 40%. Further, one significant correlation of $L_\textrm{OH} \propto L_{T_\textrm{FIR}}^{1.18\pm 0.11}$ can be found between the maser luminosity and total FIR luminosity of OHM LIRGs. Combined with previous studies, we suggest that the OHM is dominantly pumped by the FIR, instead of NIR and MIR radiation fields.