A case of simultaneous star and planet formation

TL;DR

This study presents ALMA observations of a nearly edge-on disk showing a dust gap likely carved by a young, accreting planet, alongside evidence of ongoing gas infall, indicating simultaneous star and planet formation.

Contribution

It provides direct observational evidence of a planet forming within a disk that also exhibits signs of ongoing star formation through gas infall.

Findings

Dust gap consistent with being carved by a 4-70 Jupiter mass planet.

Detection of warm gas and free-free emission inside the gap.

Evidence of ongoing gas infall from the local ISM.

Abstract

While it is widely accepted that planets are formed in protoplanetary disks, there is still much debate on when this process happens. In a few cases protoplanets have been directly imaged, but for the vast majority of systems, disk gaps and cavities -- seen especially in dust continuum observations -- have been the strongest evidence of recent or on-going planet formation. We present ALMA observations of a nearly edge-on ($i = 75^{\circ}$) disk containing a giant gap seen in dust but not in $^{12}$CO gas. Inside the gap, the molecular gas has a warm (100 K) component coinciding in position with a tentative free-free emission excess observed with the VLA. Using 1D hydrodynamic models, we find the structure of the gap is consistent with being carved by a planet with 4-70 $M_{\rm Jup}$. The coincidence of free-free emission inside the planet-carved gap points to the planet being very young and/or still accreting. In addition, the $^{12}$CO observations reveal low-velocity large scale filaments aligned with the disk major axis and velocity coherent with the disk gas that we interpret as ongoing gas infall from the local ISM. This system appears to be an interesting case where both a star (from the environment and the disk) and a planet (from the disk) are growing in tandem.