TY - JOUR
T1 - Behind the dust veil
T2 - A panchromatic view of an optically dark galaxy at z = 4.82
AU - Sillassen, Nikolaj B.
AU - Jin, Shuowen
AU - Magdis, Georgios E.
AU - Hodge, Jacqueline
AU - Gobat, Raphael
AU - Daddi, Emanuele
AU - Knudsen, Kirsten
AU - Finoguenov, Alexis
AU - Schinnerer, Eva
AU - Wang, Wei Hao
AU - Gao, Zhen Kai
AU - Weaver, John R.
AU - Algera, Hiddo
AU - Andika, Irham T.
AU - Brinch, Malte
AU - Chen, Chian Chou
AU - Cochrane, Rachel
AU - Enia, Andrea
AU - Faisst, Andreas
AU - Gillman, Steven
AU - Gomez-Guijarro, Carlos
AU - Gozaliasl, Ghassem
AU - Hayward, Chris
AU - Kokorev, Vasily
AU - Merchant, Maya
AU - Rizzo, Francesca
AU - Talia, Margherita
AU - Valentino, Francesco
AU - Blánquez-Sesé, David
AU - Koekemoer, Anton M.
AU - Magnelli, Benjamin
AU - Rich, Michael
AU - Shuntov, Marko
N1 - Publisher Copyright:
© 2025 EDP Sciences. All rights reserved.
PY - 2025
Y1 - 2025
N2 - Optically dark dusty star-forming galaxies (DSFGs) play an essential role in massive galaxy formation at early cosmic time; however, their nature remains elusive. Here, we present a detailed case study of all the baryonic components of a z = 4.821 DSFG, XS55. Selected from the ultra-deep COSMOS-XS 3 GHz map with a red SCUBA-2 450 μm/850 μm colour, XS55 was followed up with ALMA 3 mm line scans and spectroscopically confirmed to be at z = 4.821 via detections of the CO(5-4) and [CI](1-0) lines. JWST/NIRCam imaging reveals that XS55 is a F150W drop-out with a red F277W/F444W colour and a complex morphology: a compact central component embedded in an extended structure with a likely companion. XS55 is tentatively detected in X-rays with both Chandra and XMM-Newton, suggesting an active galactic nucleus nature. By fitting a panchromatic spectral energy distribution spanning from near-infrared to radio wavelengths, we reveal that XS55 is a massive main-sequence galaxy with a stellar mass of M∗ = (5 ± 1)×1010 M⊙ and a star formation rate of SFR = 540 ± 177 M⊙ yr- 1. The dust of XS55 is optically thick in the far-infrared with a surprisingly cold dust temperature of Tdust = 33 ± 2 K, making XS55 one of the coldest DSFGs at z > 4 known to date. This work unveils the nature of a radio-selected F150W drop-out, suggesting the existence of a population of DSFGs hosting active black holes embedded in optically thick dust.
AB - Optically dark dusty star-forming galaxies (DSFGs) play an essential role in massive galaxy formation at early cosmic time; however, their nature remains elusive. Here, we present a detailed case study of all the baryonic components of a z = 4.821 DSFG, XS55. Selected from the ultra-deep COSMOS-XS 3 GHz map with a red SCUBA-2 450 μm/850 μm colour, XS55 was followed up with ALMA 3 mm line scans and spectroscopically confirmed to be at z = 4.821 via detections of the CO(5-4) and [CI](1-0) lines. JWST/NIRCam imaging reveals that XS55 is a F150W drop-out with a red F277W/F444W colour and a complex morphology: a compact central component embedded in an extended structure with a likely companion. XS55 is tentatively detected in X-rays with both Chandra and XMM-Newton, suggesting an active galactic nucleus nature. By fitting a panchromatic spectral energy distribution spanning from near-infrared to radio wavelengths, we reveal that XS55 is a massive main-sequence galaxy with a stellar mass of M∗ = (5 ± 1)×1010 M⊙ and a star formation rate of SFR = 540 ± 177 M⊙ yr- 1. The dust of XS55 is optically thick in the far-infrared with a surprisingly cold dust temperature of Tdust = 33 ± 2 K, making XS55 one of the coldest DSFGs at z > 4 known to date. This work unveils the nature of a radio-selected F150W drop-out, suggesting the existence of a population of DSFGs hosting active black holes embedded in optically thick dust.
KW - Galaxies: active
KW - Galaxies: general
KW - Galaxies: ISM
U2 - 10.1051/0004-6361/202452932
DO - 10.1051/0004-6361/202452932
M3 - Journal article
AN - SCOPUS:85217079716
SN - 0004-6361
VL - 693
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A309
ER -