Volume 624, April 2019
|Number of page(s)||23|
|Published online||26 April 2019|
CO, H2O, H2O+ line and dust emission in a z = 3.63 strongly lensed starburst merger at sub-kiloparsec scales⋆
European Southern Observatory, Alonso de Córdova 3107, Casilla, 19001 Vitacura, Santiago, Chile
2 Institut d’Astrophysique de Paris, Sorbonne Université, CNRS, UMR 7095, 98 bis bd Arago, 75014 Paris, France
3 Institut d’Astrophysique Spatiale, CNRS UMR 8617, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France
4 Purple Mountain Observatory/Key Lab of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210034, PR China
5 European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching, Germany
6 Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
7 Centre for Extragalactic Astronomy, Durham University, Department of Physics, South Road, Durham, DH1 3LE, UK
8 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
9 Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
10 Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin-d’Hères, France
11 Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
12 School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
13 School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA, UK
14 Department of Physics & Astronomy, University of Iowa, Iowa City, IA 52245, USA
15 Universidad de Alcalá, Departamento de Física y Matemáticas, Campus Universitario, 28871 Alcalá de Henares, Madrid, Spain
16 Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso, Chile
17 Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
18 Instituto de Astrofísica de Canarias, C/Vía Láctea, s/n, 38205 San Cristóbal de La Laguna, Tenerife, Spain
19 Universidad de La Laguna, Dpto. Astrofísica, 38206 San Cristóbal de La Laguna, Tenerife, Spain
20 Department of Astronomy, Cornell University, 220 Space Sciences Building, Ithaca, NY 14853, USA
21 Leiden Observatory, Leiden University, Post Office Box 9513, 2300 RA Leiden, The Netherlands
Accepted: 28 February 2019
Using the Atacama Large Millimeter/submillimeter Array (ALMA), we report high angular-resolution observations of the redshift z = 3.63 galaxy H-ATLAS J083051.0+013224 (G09v1.97), one of the most luminous strongly lensed galaxies discovered by the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). We present 0.″2−0.″4 resolution images of the rest-frame 188 and 419 μm dust continuum and the CO(6–5), H2O(211−202), and Jup = 2 H2O+ line emission. We also report the detection of H2O(211−202) in this source. The dust continuum and molecular gas emission are resolved into a nearly complete ∼1.″5 diameter Einstein ring plus a weaker image in the center, which is caused by a special dual deflector lensing configuration. The observed line profiles of the CO(6–5), H2O(211−202), and Jup = 2 H2O+ lines are strikingly similar. In the source plane, we reconstruct the dust continuum images and the spectral cubes of the CO, H2O, and H2O+ line emission at sub-kiloparsec scales. The reconstructed dust emission in the source plane is dominated by a compact disk with an effective radius of 0.7 ± 0.1 kpc plus an overlapping extended disk with a radius twice as large. While the average magnification for the dust continuum is μ ∼ 10−11, the magnification of the line emission varies from 5 to 22 across different velocity components. The line emission of CO(6–5), H2O(211−202), and H2O+ have similar spatial and kinematic distributions. The molecular gas and dust content reveal that G09v1.97 is a gas-rich major merger in its pre-coalescence phase, with a total molecular gas mass of ∼1011 M⊙. Both of the merging companions are intrinsically ultra-luminous infrared galaxies (ULIRGs) with infrared luminosities LIR reaching ≳4 × 1012 L⊙, and the total LIR of G09v1.97 is (1.4 ± 0.7)×1013 L⊙. The approaching southern galaxy (dominating from V = −400 to −150 km s−1 relative to the systemic velocity) shows no obvious kinematic structure with a semi-major half-light radius of as = 0.4 kpc, while the receding galaxy (0 to 350 km s−1) resembles an as = 1.2 kpc rotating disk. The two galaxies are separated by a projected distance of 1.3 kpc, bridged by weak line emission (−150 to 0 km s−1) that is co-spatially located with the cold dust emission peak, suggesting a large amount of cold interstellar medium (ISM) in the interacting region. As one of the most luminous star-forming dusty high-redshift galaxies, G09v1.97 is an exceptional source for understanding the ISM in gas-rich starbursting major merging systems at high redshift.
Key words: galaxies: high-redshift / galaxies: ISM / gravitational lensing: strong / submillimeter: galaxies / radio lines: ISM / ISM: molecules
Reduced images and datacubes are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A138
© ESO 2019
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