Revealing the complex nature of the strong gravitationally lensed system H-ATLAS J090311.6+003906 using ALMA

Author(s): Simon Dye, C. Furlanetto, A. Mark Swinbank, C. Vlahakis, J. W. Nightingale, Helmut Dannerbauer
Abstract: We have modelled Atacama Large Millimetre/sub-millimetre Array (ALMA) long baseline imaging of the strong gravitational lens system H-ATLAS J090311.6+003906 (SDP.81). We have reconstructed the distribution of band 6 and 7 continuum emission in the z = 3.042 source and determined its kinematic properties by reconstructing CO(5-4) and CO(8-7) line emission in bands 4 and 6. The continuum imaging reveals a highly non-uniform distribution of dust with clumps on scales of ~ 200 pc. In contrast, the CO line emission shows a relatively smooth, disc-like velocity field which is well fitted by a rotating disc model with an inclination angle of (40 ± 5)° and an asymptotic rotation velocity of 320 km s^-1. The inferred dynamical mass within 1.5 kpc is (3.5 ± 0.5) × 10¹⁰ M_⊙ which is comparable to the total molecular gas masses of (2.7 ± 0.5) × 10¹⁰ M_⊙ and (3.5 ± 0.6) × 10¹⁰ M_⊙ from the dust continuum emission and CO emission, respectively. Our new reconstruction of the lensed Hubble Space Telescope near-infrared emission shows two objects which appear to be interacting, with the rotating disc of gas and dust revealed by ALMA distinctly offset from the near-infrared emission. The clumpy nature of the dust and a low value of the Toomre parameter of Q ~ 0.3 suggest that the disc is in a state of collapse. We estimate a star formation rate in the disc of 470 ± 80 M_⊙ yr^-1 with an efficiency ~ 65 times greater than typical low-redshift galaxies. Our findings add to the growing body of evidence that the most infrared luminous, dust obscured galaxies in the high-redshift Universe represent a population of merger-induced starbursts.
Organisation(s): Department of Astrophysics
External organisation(s): University of Nottingham, European Southern Observatory (Chile), Durham University
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 452
Pages: 2258 - 2268
No. of pages: 11
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stv1442
Publication date: 09-2015
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/revealing-the-complex-nature-of-the-strong-gravitationally-lensed-system-hatlas-j0903116003906-using-alma(3f1b23c3-d8aa-49d8-807d-cf19dd0dbe93).html

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