Letter to the Editor

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

¹ Department of Physics, University of Crete, 70013 Heraklion, Greece
² Institute of Astrophysics, Foundation for Research and Technology – Hellas (FORTH), 70013 Heraklion, Greece
³ School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
⁴ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Müchen, Germany
⁵ Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain
⁶ Universidad de La Laguna, Dpto. Astrofísica, E-38206 La Laguna, Tenerife, Spain
⁷ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
⁸ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA
⁹ IPAC, California Institute of Technology, 1200 E. California Boulevard, Pasadena, 91125 CA, USA
¹⁰ School of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
¹¹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, I-40129 Bologna, Italy
¹² Department of Physics, Winona State University, 175 West Mark Street, Winona, 55987 MN, United States
¹³ Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile
¹⁴ Las Campanas Observatory, Carnegie Institution of Washington, Raúl Bitrán 1200, La Serena, Chile
¹⁵ Department of Physics, Northwestern College, 101 7th St SW, Orange City, IA 51041, USA
¹⁶ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
¹⁷ University of Chinese Academy of Sciences, Beijing 100049, China
¹⁸ Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS, Beijing 100101, China
¹⁹ Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China
²⁰ Centre for Space Research, North-West University, Potchefstroom 2520, South Africa
²¹ Department of Physics, College of Natural and Computational Science, Debre Berhan University, P.O. Box 445 Debre Berhan, Ethiopia

^⋆ Corresponding author; rfernandez@physics.uoc.gr

Received: 28 November 2024
Accepted: 13 February 2025

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.