2007A&A...466..831S

To shed more light on the integrated FIR properties of galaxies, the ≃2000 compact sources in the ISOPHOT Serendipity Survey associated with identified galaxies are investigated statistically. They provide the only sample large enough to determine the FIR properties such as dust temperatures and masses, FIR luminosities, and HI-to-dust ratios not only for the group as a whole, but also divided into several subgroups of different Hubble types. Only with this catalog, the high flux end of the 170µm galaxy number counts can be established, which is crucial as a complement to the much deeper ISOPHOT studies at this wavelength in much smaller sky areas. The differential distributions of integrated FIR properties and the cumulative number counts are analysed. The galaxy list of the ISOPHOT Serendipity Survey has a 170µm completeness limit of ≃2Jy. The statistical analysis confirmed that the F_170µm/F_100µm flux ratios peak at ≃1, corresponding to a dust color temperature of ≃20K. FIR luminosities and dust masses cover a large range with peaks near L_1–1000=10^10.5±1L_☉ and M_Dust≃10^7.5±0.5M_☉, respectively. HI-to-dust ratios range from ≃10 and ≃10⁴, rendering the notion of fiducial HI-to-dust ratio for conversion between gas and dust masses almost useless. The latest models of the cumulative 170µm number counts are in reasonable agreement with the deep as well as the shallow surveys from ISO up to fluxes of ≃50Jy.