Detailed lens modeling and kinematics of the submillimeter galaxy G09v1.97. An analysis of CO, H2O, H2O+, and dust continuum emission

Abstract

The formation mechanisms of intensely starbursting galaxies at high redshift remain unknown. One possible mechanism for triggering these starbursts is mergers and interactions, but detecting these at high redshift remains a challenge. Observations of high-redshift gravitationally lensed galaxies enable studies of the interstellar medium and environment of these extreme starbursts in detail. We used high angular resolution observations of dust continuum, CO(6-5), H2O(211-202), and H2O+(202-111) emission to constrain the ongoing processes in the z = 3.63 gravitationally lensed submillimeter galaxy H-ATLAS J083051.0+013224 (G09v1.97). We used PyAutoLens to create a de-magnified source plane CO(6-5) emission line cube and performed kinematic modeling using 3DBarolo. Additionally, we investigated the properties of the continuum and molecular line emission in the source plane. We find that the regions of CO(6-5) and H2O(211-202) emission match closely in the source plane but that the dust continuum emission is more compact. We find that our lens modeling results do not require more than one source, contrary to what has been found in previous studies. Instead, we find that G09v1.97 resembles a rotating disk with Vmax/sigma = 2.8 +/- 0.4 with evidence for residual emission indicative of non-circular motions such as outflows, tidal tails, or an additional background galaxy. We suggest that the origin of the non-circular motions may be associated with a bi-conical outflow, a tidal tail from an interaction, or indicate the possible presence of an additional galaxy. We calculate the dynamical mass, gas mass, star-formation rate, and depletion time for G09v1.97 and find a high star-formation rate and low gas depletion time. In combination, this suggests that G09v1.97 has recently undergone an interaction, triggering intense star formation, and is in the process of settling into a disk.