Abstract

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 mu m dust continuum and the CO(6-5), H2O(2(11)-2(02)), and J(up) = 2H(2)O(+) line emission. We also report the detection of (H2O)-O-18(2(11)-2(02)) in this source. The dust continuum and molecular gas emission are resolved into a nearly complete similar to 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(2(11)-2(02)), and J(up) = 2H(2)O(+) 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 mu similar to 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(2(11)-2(02)), 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 similar to 10(11) M-circle dot Both of the merging companions are intrinsically ultra-luminous infrared galaxies (ULIRGs) with infrared luminosities L-IR reaching greater than or similar to 4 x 10(12) L-circle dot, and the total L-IR of G09v1.97 is (1.4 +/- 0.7) x 10(13) L-circle dot. 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 a(s) = 0.4 kpc, while the receding galaxy (0 to 350 km s(-1)) resembles an a(s) = 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.