Infrared spectral energy distribution decomposition of WISE-selected, hyperluminous hot dust-obscured galaxies

Abstract

We utilize a Bayesian approach to fit the observed mid-IR-to-submm/mm spectral energy distributions (SEDs) of 22 WISE-selected and submm-detected, hyperluminous hot dust-obscured galaxies. By adopting the Torus+GB model, we decompose the observed IR SEDs of Hot DOGs into torus and cold dust components. The main results are: 1) Hot DOGs in our submm-detected sample are hyperluminous, with torus emission dominating the IR energy output. However, cold dust emission is non-negligible, averagely contributing ~24% of total IR luminosity. 2) Compared to QSO and starburst SED templates, the median SED of Hot DOGs shows the highest luminosity ratio between mid-IR and submm at rest-frame, while it is very similar to that of QSOs at 10-50um suggesting that the heating sources of Hot DOGs should be buried AGNs. 3) Hot DOGs have both high dust temperatures ~73K and IR luminosity of cold dust. The T-L relation of Hot DOGs suggests that the increase in IR luminosity for Hot DOGs is mostly due to the increase of the dust temperature, rather than dust mass. Hot DOGs have lower dust masses than those of submillimeter galaxies (SMGs) and QSOs within the similar redshift range. Both high IR luminosity of cold dust and relatively low dust mass in Hot DOGs can be expected by their relatively high dust temperatures. 4) Hot DOGs have high dust covering factors, which deviate the previously proposed trend of the dust covering factor decreasing with increasing bolometric luminosity. Finally, we can reproduce the observed properties in Hot DOGs by employing a physical model of galaxy evolution. The result suggests that Hot DOGs may lie at or close to peaks of both star formation and black hole growth histories, and represent a transit phase during the evolution of massive galaxies, transforming from the dusty starburst dominated phase to the optically bright QSO phase. (abridged)