The spectral energy distribution of the hyperluminous, hot dust-obscured galaxy W2246$-$0526

Abstract

Hot dust-obscured galaxies (Hot DOGs) are a luminous, dust-obscured population recently discovered in the WISE All-Sky survey. Multiwavelength follow-up observations suggest that they are mainly powered by accreting supermassive black holes (SMBHs), lying in dense environments, and being in the transition phase between extreme starburst and UV-bright quasars. Therefore, they are good candidates for studying the interplay between SMBHs, star formation and environment. W2246$-$0526 (thereafter, W2246), a Hot DOG at $z\sim4.6$, has been taken as the most luminous galaxy known in the Universe. Revealed by the multiwavelength images, the previous Herschel SPIRE photometry of W2246 is contaminated by a foreground galaxy (W2246f), resulting in an overestimation of its total IR luminosity by a factor of about 2. We perform the rest-frame UV/optical-to-far-IR spectral energy distribution (SED) analysis with SED3FIT and re-estimate its physical properties. The derived stellar mass $M_\star = 4.3\times10^{11}~M_\odot$ makes it be among the most massive galaxies with spectroscopic redshift $z>4.5$. Its structure is extremely compact and requires an effective mechanism to puff-up. Most of ($>95\%$) its IR luminosity is from AGN torus emission, revealing the rapid growth of the central SMBH. We also predict that W2246 may have a significant molecular gas reservoir based on the dust mass estimation.