Volume 586, February 2016
|Number of page(s)||5|
|Published online||04 February 2016|
An ALMA view of the interstellar medium of the z = 4.77 lensed starburst SPT-S J213242-5802.9
1 European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching, Germany
2 Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
3 Cavendish Laboratory, University of Cambridge, JJ Thompson Ave, Cambridge CB3 0HA, UK
4 Dalhousie University, Halifax, Nova Scotia, Canada
5 Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
6 Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
7 Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547, USA
8 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
9 Infrared Processing and Analysis Center, California Institute of Technology, MC 220-6, Pasadena, CA 91125, USA
10 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
11 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
12 Department of Astronomy and Department of Physics, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA
13 Department of Physiscs, Oxford University, Denis Wilkinson Building, Keble Road, Oxford, OX1 3RH, UK
Received: 13 November 2015
Accepted: 6 January 2016
We present ALMA detections of the [NII] 205 μm and CO(12−11) emission lines, and the tentative detection of [CI] 3P1–3P0 for the strongly lensed (μ = 5.7 ± 0.5) dusty, star-forming galaxy SPT-S J213242-5802.9 (hereafter SPT2132-58) at z = 4.77. The [NII] and CO(12−11) lines are detected at 11.5 and 8.5σ levels, respectively, by our band 6 observations. The [CI] line is detected at 3.2σ after a reanalysis of existing band 3 data. The [CI] luminosity implies a gas mass of (3.8 ± 1.2) × 1010M⊙, and, consequently, a very short depletion timescale of 34 ± 13 Myr and a CO luminosity to gas mass conversion factor αCO of 1.0 ± 0.3 M⊙ (K km s-1 pc2)-1. SPT2132-58 is an extreme starburst with an intrinsic star formation rate of 1100 ± 200 M⊙/yr. We find a [CII]/[NII] ratio of 26 ± 6, which is the highest ratio reported at z > 4. This suggests that SPT2132-58 hosts an evolved interstellar medium (0.5 Z⊙< Z < 1.5 Z⊙), which may be dominated by photodissociation regions. The CO(2−1) and CO(5−4) transitions have lower CO to far-infrared ratios than local and high-redshift samples, while CO(12−11) is similar to these samples, suggesting the presence of an additional very excited component or an active galactic nucleus.
Key words: galaxies: starburst / galaxies: ISM / galaxies: high-redshift / galaxies: star formation / submillimeter: galaxies
© ESO, 2016
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