Spatially resolved dust properties over 50 kpc in a hyperluminous galaxy merger at z = 4.6

Abstract

We present spatially resolved dust-continuum ALMA observations from rest frame ∼60 to ∼600 μm (bands 3–10) of the hyperluminous hot dust-obscured galaxy (hot DOG) WISE J224607.6–052634.9 (W2246–0526), at redshift z = 4.6. W2246–0526 is interacting with at least three companion galaxies, forming a system connected by tidal streams. We model the multiwavelength ALMA observations of the dust continuum using a modified blackbody, from which we derive the dust properties (mass, emissivity index, area of the emitting region, and temperature) in the hot DOG and in resolved structures across a region of nearly ∼50 kpc. The peak temperature at the location of the hot DOG, ∼110 K, is likely the consequence of heating by the central quasar. The dust temperature drops to ∼40 K at a radius of ∼8 kpc, suggesting that heating by the quasar beyond that distance is non-dominant. The dust in the connecting streams between the host and companion galaxies is at temperatures between 30 and 40 K, typical of starburst galaxies, suggesting it is most likely heated by recent in situ star formation. This is the first time that dust properties have been spatially resolved over several tens of kiloparsec in a galaxy system beyond Cosmic Noon; this is more than six times the scales previously probed in galaxies at these redshifts.