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

Journal article, 2026

Context. While the formation mechanisms of intensely starbursting galaxies at high redshift remain unknown, one possible mechanism for producing these intense rates of star formation is via mergers and interactions. However, detecting these at high redshift remains a challenge. Observations of high-redshift gravitationally lensed galaxies provide a way to study the interstellar medium and environment of these extreme starbursts in detail. Aims. We aim to use 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). Methods. We used the sophisticated lens modeling software PyAutoLens to perform both parametric and nonparametric source modeling. We created a demagnified source plane CO(6−5) emission line cube and performed the kinematic modeling using ^3DBarolo. Additionally, we investigated the properties of the continuum and molecular line emission in the source plane. Results. We find that the regions of CO(6−5) and H2O(211 − 202) emission are closely matched 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/σ̄ = 2.8 ± 0.4, along with evidence of residual emission indicative of noncircular motions such as outflows, tidal tails, or an additional background galaxy. Conclusions. We suggest that the origin of the noncircular motions might be associated with a biconical outflow or a tidal tail from an interaction; alternatively, this might indicate the possible presence of an additional galaxy. We calculated the dynamical mass, gas mass, star formation rate, and depletion time for G09v1.97, along with 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, while also being in the process of settling into a disk.