Hiding behind a curtain of dust: Gas and dust properties of an ultra-luminous strongly-lensed z=3.75 galaxy behind the Milky Way disc
Artikel i vetenskaplig tidskrift, 2026
We present a detailed analysis of J154506, a strongly lensed submillimetre galaxy (SMG) behind the Lupus-I molecular cloud, and a characterisation of its physical properties using a combination of new and archival data, including VLT/MUSE and FORS2 optical data. We identify two high-significance (S/N > 5) emission lines at 97.0 and 145.5 GHz, corresponding to CO(4-3) and CO(6-5), respectively, in spectral scans from the Atacama Compact Array (ACA) and the Large Millimetre Telescope (LMT), as well as the [CII] 158 mu m fine-structure line at 400 GHz observed with the Atacama Pathfinder Experiment (APEX). These detections yield a spectroscopic redshift of z(spec) = 3.7515 +/- 0.0005. We also report the detection of [CI], HCN(4-3), and two H2O+ transitions, further confirming the redshift and providing insights into the physical properties of J154506. By modelling sub-arcsecond resolution (0.75 '') ALMA Band 6 and 7 continuum data in the uv-plane, we derive an average magnification factor of 6.0 +/- 0.4, and our analysis reveals a relatively cold dust (38 K) in a starburst galaxy (similar to 900 M-circle dot yr(-1)) with a high intrinsic dust mass (similar to 2.5 x 10(9) M-circle dot) and infrared (IR) luminosity (similar to 6 x 10(12) L-circle dot). Non-local thermodynamic equilibrium radiative transfer modelling of the joint dust spectral energy distribution (SED) and CO line excitation suggests the dust continuum emission is primarily associated with relatively diffuse regions with molecular gas densities of 10(2)-10(4) cm(-3), rather than compact, high-pressure environments typical of extreme starbursts or active galactic nuclei (AGNs). This interpretation is supported by the close-to-unity ratio between the dust and gas kinetic temperatures, which argues against highly energetic heating mechanisms. The CO excitation ladder peaks close to CO(5-4) and is dominated by slightly denser molecular gas. Our results underscore the unique power of far-IR and submillimetre observations to both uncover and characterise scarce, strongly lensed, high-redshift galaxies, even when they are obscured by foreground molecular clouds.
gravitational lensing: strong
galaxies: starburst
galaxies: high-redshift
submillimeter: galaxies
Författare
Belen Alcalde Pampliega
Universidad Diego Portales
Square Kilometre Array, UK
ESO Vitacura
Kevin C. Harrington
National Astronomical Observatory of Japan
ESO Vitacura
Atacama Large Millimeter-submillimeter Array (ALMA)
Universidad Diego Portales
Aristeidis Amvrosiadis
Durham University
Manuel Aravena
Universidad Diego Portales
Millenium Nucleus for Galaxies (MINGAL)
Min S. Yun
University of Massachusetts
Hugo Messias
ESO Vitacura
Atacama Large Millimeter-submillimeter Array (ALMA)
Antonio Hernan-Caballero
Centro de Estudios de Física del Cosmos de Aragón (CEFCA)
Leindert Boogaard
Universiteit Leiden
Axel Weiss
Max-Planck-Gesellschaft
Benjamin Beauchesne
Durham University
Alejandro Santamaria-Miranda
Universidad de Chile (UCH)
Monica Ivette Rodriguez
Instituto de Radioastronomía Milimétrica
Eric Jimenez-Andrade
Universidad Nacional Autónoma de México
Manuel Solimano
Universidad Diego Portales
James Lowenthal
Smith College
Patrick Kamieneski
Arizona State University
Q. Daniel Wang
University of Massachusetts
Chentao Yang
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
Amit Vishwas
Cornell University
Pascale Hibon
ESO Vitacura
Brenda Frye
University of Arizona
Jorge Gonzalez-Lopez
Universidad Diego Portales
Yiqing Song
ESO Vitacura
Meghana Killi
Universidad Diego Portales
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 706 A174Ämneskategorier (SSIF 2025)
Atom- och molekylfysik och optik
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/202556106