A study of the infrared characteristics of host IRAS sources with OH megamasers

Abstract

OH megamasers are the most luminous cosmic maser sources known. So far powerful OH maser emission has been discovered from 90 extragalactic objects. An important observational characteristic of the OH megamaser sources is their relationship between L(OH) and L(IR). We study the relationship between log L(OH) and log L(IR) for the 67 OH megamaser sources for which there are data on L(OH) and L(IR). Accounting for Malmquist bias, the relationship L(OH) ∼ L(IR)1.41 is obtained. We use the largest sample currently available to study the relationship between L(OH) and L(IR) for OH megamaser sources. Our results agree with Kandalian's results within the uncertainties. The infrared properties of the host IRAS sources with OH megamasers are also studied. The most striking features are the anticorrelation of S(12 μm)/S(25 μm) versus S(60 μm)/ S(100 μm) and the correlation of S(12 μm)/S(25μm) versus 5(25 μm)/S(60 μm). They are consistent with Henkel, Wouterlooy & Bally's finding that S(12 μm)/S(25 μm) is anticorrelated with S(60 μm)/S(100 μm), but are the opposite of Henkel et al.'s result that S(12 μm)/ S(25 μm) is correlated with S(25 μm)/μ(60 μm). This is an interesting difference. Our colour-colour plots suggest that the peak of the infrared spectra of our sample of OH sources is at a longer wavelength than the peak in the sample of Henkel et al. This suggests that infrared radiation from our sample is dominated by emission from material at greater separations from the central source.