CO, H 2 O, H 2 O + line and dust emission in a z = 3.63 strongly lensed starburst merger at sub-kiloparsec scales

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(2 11-2 02) and J up = 2 H2O + line emission. We also report the detection of H 18 2 O(2 11-2 02) 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(2 11-2 02) and J up = 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. The total intrinsic infrared luminosity, L IR , of G09v1.97 is (1.4 ± 0.7) × 10^13 L_sol and is a hyper-luminous infrared galaxy. 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 ∼ 10^11 Msol. Both of the merging companions are intrinsically ultra-luminous infrared galaxies (ULIRGs) with L_IR reaching 4 × 10^12 Lsol. The approaching southern galaxy (dominating from V = −400 to −150 km/s relative to the systemic velocity) shows no obvious kinematic structure with a half-light radius Reff = 0.4 kpc, while the receding galaxy (0 to 350 km s −1) resembles a R eff = 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