Abstract

Hints of planet formation have been independently reported within the gap of the disc around 2MASS-J16120668-301027 from millimetre continuum, infrared, and H alpha observations. In this work, we present new evidence for ongoing planet formation based on Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations, detecting 0.87 mm dust continuum emission together with (CO)-C-12 (J = 3-2) and (CO)-C-13 (J = 3-2) line emission. Visibility modelling of the continuum data reveals an inner disc and two dust rings peaking at 23 and 75 au. The continuum morphology is better reproduced by an eccentric disc model (e similar to 0.1) than by an axisymmetric disc. We further investigate the gas kinematics through modelling of the (CO)-C-12 channel maps. The residual line-width map shows a localized increase in velocity dispersion at the position of a previously reported circumplanetary disc candidate (deprojected radius similar to 32 au, position angle similar to 170(degrees)) and along its orbit. This signal is spatially coincident with kink-like features and a transition from sub-Keplerian to super-Keplerian velocities. In addition, the velocity residual map exhibits an arc-like structure extending outward from the planet candidate, while the gas kinematics - despite substantial uncertainties - is consistent with inflow towards the candidate's orbital radius. The observed increase in velocity dispersion agrees with predictions from planet-disc interaction simulations, which produce enhanced turbulence both at the planet location and along its orbital path. Taken together, the continuum morphology and gas kinematic signatures provide compelling new evidence for ongoing planet formation within the disc gap.