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CO, H2O, H2O+ line and dust emission in a z = 3.63 strongly lensed starburst at sub-kiloparsec scales

Yang, C., Gavazzi, R., Beelen, A., Cox, P., Omont, A., Lehnert, M. D., Gao, Y., Ivison, R. J., Swinbank, A. M., Barcos-Munoz, L., Neri, R., Cooray, A., Dye, S., Eales, S. ORCID:, Fu, H., Gonzalez-Alfonso, E., Ibar, E., Michaowski, M. J., Nayyeri, H., Negrello, M. ORCID:, Nightingale, J., Pérez-Fournon, I., Riechers, D. A., Smail, I. and van der Werf, P. 2019. CO, H2O, H2O+ line and dust emission in a z = 3.63 strongly lensed starburst at sub-kiloparsec scales. Astronomy and Astrophysics 624 , A138. 10.1051/0004-6361/201833876

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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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: EDP Sciences
ISSN: 0004-6361
Date of First Compliant Deposit: 18 March 2019
Date of Acceptance: 28 February 2019
Last Modified: 21 May 2023 06:55

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