Volume 631, November 2019
|Number of page(s)||8|
|Published online||15 November 2019|
A dense, solar metallicity ISM in the z = 4.2 dusty star-forming galaxy SPT 0418−47⋆
European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching, Germany
2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
3 Aix Marseille University, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France
4 Department of Astronomy and Physics, Saint Mary’s University, Halifax, NS B3H 3C3, Canada
5 Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 4R2, Canada
6 Departamento de Ciencias Fisicas, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago, Chile
7 Millennium Institute of Astrophysics (MAS), Nuncio Monseñor Sotero Sanz 100, Providencia, Santiago, Chile
8 Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
9 Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green St., Urbana, IL 61801, USA
10 National Research Council, Herzberg Astronomy and Astrophysics, Victoria, BC, Canada
11 Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
12 Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547, USA
13 Department of Astronomy, Cornell University, Ithaca, NY 14853, USA
Accepted: 26 September 2019
We present a study of six far-infrared fine structure lines in the z = 4.225 lensed dusty star-forming galaxy SPT 0418−47 to probe the physical conditions of its interstellar medium (ISM). In particular, we report Atacama Pathfinder EXperiment (APEX) detections of the [OI] 145 μm and [OIII] 88 μm lines and Atacama Compact Array (ACA) detections of the [NII] 122 and 205 μm lines. The [OI] 145 μm/[CII] 158 μm line ratio is ∼5× higher compared to the average of local galaxies. We interpret this as evidence that the ISM is dominated by photo-dissociation regions with high gas densities. The line ratios, and in particular those of [OIII] 88 μm and [NII] 122 μm imply that the ISM in SPT 0418−47 is already chemically enriched to nearly solar metallicity. While the strong gravitational amplification was required to detect these lines with APEX, larger samples can be observed with the Atacama Large Millimeter/submillimeter Array (ALMA), and should allow observers to determine if the dense, solar metallicity ISM is common among these highly star-forming galaxies.
Key words: galaxies: ISM / galaxies: high-redshift / submillimeter: galaxies / submillimeter: ISM
The spectra in Fig. 1 are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/631/A167
© ESO 2019
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