Issue |
A&A
Volume 695, March 2025
|
|
---|---|---|
Article Number | L18 | |
Number of page(s) | 9 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202453279 | |
Published online | 21 March 2025 |
Letter to the Editor
ALMA 360 parsec, high-frequency observations reveal warm dust in the center of a z = 6.9 quasar
1
Departement d’Astronomie, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
2
Max-Planck Institute for Astronomy, Königstuhl 17, 69118 Heidelberg, Germany
3
Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
4
Dipartimento di Fisica “G. Occhialini”, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3 I-20126 Milano, Italy
5
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903, USA
6
Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden, The Netherlands
⋆ Corresponding author; romain.meyer@unige.ch
Received:
3
December
2024
Accepted:
20
February
2025
The temperature of the cold dust in z > 6 galaxies is a potential tracer of the presence of an active galactic nucleus (AGN) and stellar feedback. This is also the dominant source of uncertainty in inferring properties from the far-infrared (FIR) emission of these galaxies. We present the first resolved dust temperature map in a z > 6 quasar host galaxy. We combined new 360 parsec (pc) resolution ALMA Band 9 continuum observations with 190 pc Band 6 observations from the literature to derive the dust temperature and opacity at 0.1 < r < 0.5 kpc scales in a z = 6.9 luminous quasar host galaxy (J2348–3054). We find that the dust temperature (and opacity) increases at the center (r < 216 pc) of the galaxy up to Td = 73 − 88 K, potentially rising up to Td < 149 K at r < 110 pc. The combination of the resolved and integrated FIR spectral energy distribution (SED) further reveal a dust temperature gradient and a significant contribution of the AGN hot dust torus at νobs ≳ 700 GHz. By taking into account the torus contribution and resolved optically thick emission, we derived the total IR luminosity (LTIR = 8.78 ± 0.10) × 1012 L⊙) and corresponding star formation rate (SFR = 1307 ± 15 M⊙yr-1), which are at least a factor of ∼3.6 (∼0.56 dex) lower than previous measurements based on the assumption of optically thin emission. We compared the resolved dust temperature, mass, and IR luminosity profiles to simulations where they are only reproduced by models that include the AGN radiation heating the dust in the center of the galaxy. Our observations provide evidence that dust in J2348–3054 cannot be assumed to be uniformly cold and optically thin. Whether J2348–3054 is representative of the larger population of high-redshift quasars and galaxies remains to be determined with future dedicated high-resolution and high-frequency ALMA observations.
Key words: galaxies: high-redshift / galaxies: ISM / quasars: general / galaxies: star formation / submillimeter: galaxies
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.