The ALMA-CRISTAL survey: Dust temperature and physical conditions of the interstellar medium in a typical galaxy at z = 5.66

¹ Departamento de Astronomía, Universidad de Concepción, Barrio Universitario, Concepción, Chile
² Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Santiago, 7820436 Chile
³ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, Santiago, 8370191 Chile
⁴ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903 USA
⁵ INAF-Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
⁶ Chemistry Department, Sapienza University of Rome, P.le A. Moro, 00185 Rome, Italy
⁷ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Manchester, M13 9PL UK
⁸ International Centre for Radio Astronomy Research, ICRAR M468, 35 Stirling Hwy, Crawley, 6009 Western Australia
⁹ Sterrenkundig Observatorium, Ghent University, Krijgslaan 281 - S9, B9000 Ghent, Belgium
¹⁰ Department of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT UK
¹¹ Institute of Astrophysics, Foundation for Research and Technology-Hellas (FORTH), Heraklion, GR-70013 Greece
¹² School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
¹³ Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
¹⁴ Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526 Hiroshima, Japan
¹⁵ Department of Astronomy, School of Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo, 181-8588 Japan
¹⁶ Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033 Japan
¹⁷ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588 Japan
¹⁸ Max Planck Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany
¹⁹ Departamento Física Teórica y del Cosmos, Universidad de Granada, E-18071 Granada, Spain
²⁰ Instituto Universitario Carlos I de Física Teórica y Computacional, Universidad de Granada, E-18071 Granada, Spain
²¹ Department of Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, TX, 77843-4242 USA
²² Dipartimento di Fisica e Astronomia, Universita di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy
²³ INAF – OAS, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Gobetti 93/3, I-40129 Bologna, Italy
²⁴ Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA, 15260 USA
²⁵ Faculty of Engineering, Hokkai-Gakuen University, Toyohira-ku, Sapporo, 062-8605 Japan
²⁶ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge, CB3 0HA UK
²⁷ Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge, CB3 0HE UK
²⁸ Scuola Normale Superiore, Piazza dei Cavalieri 7, I- 50126 Pisa, Italy
²⁹ Las Campanas Observatory, Carnegie Institution of Washington, Casilla 601, La Serena, Chile

^⋆⋆ Corresponding author; vvillanueva@astro-udec.cl

Received: 12 July 2024
Accepted: 18 September 2024

Abstract

We present new λ_rest = 77 μm dust continuum observations from the Atacama Large Millimeter/submillimeter Array of HZ10 (CRISTAL-22). This dusty main sequence galaxy at z = 5.66 was observed as part of the [CII] Resolved Ism in STar-forming Alma Large program (CRISTAL). The high angular resolution of the ALMA Band 7 and new Band 9 data (∼0′′​​.4) reveals the complex structure of HZ10, which comprises two main components (HZ10-C and HZ10-W), along with a bridge-like dusty emission between them (i.e., “the bridge”). Using a modified blackbody function to model the dust spectral energy distribution (SED), we constrained the physical conditions of the interstellar medium (ISM) and its variations among the different components identified in HZ10. We find that HZ10-W (the more UV-obscured component) has an SED dust temperature of T_SED ∼ 51.2 ± 13.1 K; this was found to be ∼5 K higher (which is statistically insignificant; i.e., less than 1σ) than that of the central component and previous global estimations for HZ10. Our new ALMA data allow us to reduce the uncertainties of global T_SED measurements by a factor of ∼2.3, compared to previous studies. The HZ10 components have [CII]-to-far-infrared (FIR) luminosity ratios and FIR surface densities values that are consistent with local starburst galaxies. However, HZ10-W shows a lower [CII]/FIR ratio compared to the other two components (albeit still within the uncertainties), which may suggest a harder radiation field destroying polycyclic aromatic hydrocarbon associated with [CII] emission (e.g., active galactic nuclei or young stellar populations). While HZ10-C appears to follow the tight IRX-β_UV relation seen in local UV-selected starburst galaxies and high-z star-forming galaxies, we find that both HZ10-W and the bridge depart from this relation and are well described by dust-screen models with holes in front of a hard UV radiation field. This suggests that the UV emission, which is likely coming from young stellar populations, is strongly attenuated in the “dustier” components of the HZ10 system.