Infrared Characters of Host Galaxies with H₂O Megamaser

Infrared characters of all the host galaxies with H₂O megamaser have been studied. The most striking feature is anticorrelation of S(60)/S(100) versus S(12)/S(25), and S(25)/S(60) versus S(12)/S(25). The anticorrelation in flux density ratio can been explained by coexistence of large and very small dust particles. The latter, which are heated by absorption of single photon, are believed to be resposible for bulk of 12 μm radiation. If the photon energy of the host galaxy is small, this implies large S(12)/S(25) and small S(60)/S(100). However, when photon energy density becomes larger, the infrared spectrum will peak at wavelengths ≤ 100μm and enhance emission at 25μm. As a consequence small S(12)/S(25) and large S(60)/S(100) are observed.