ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) VI: Accretion shocks in the disk of DG Tau and HL Tau

TL;DR

This study uses high-resolution ALMA observations to identify accretion shocks caused by inflowing material in the disks of young stars DG Tau and HL Tau, revealing their impact on disk chemistry and evolution.

Contribution

It provides the first detailed evidence of accretion shocks in the disks of DG Tau and HL Tau using SO and SO2 emissions, highlighting their role in disk chemistry.

Findings

SO and SO2 emissions originate at streamer-disk intersections.

Accretion shocks are confined to specific disk regions in these sources.

Shocks can influence disk chemical composition and mass content.

Abstract

Planet-forming disks are not isolated systems. Their interaction with the surrounding medium affects their mass budget and chemical content. In the context of the ALMA-DOT program, we obtained high-resolution maps of assorted lines from six disks that are still partly embedded in their natal envelope. In this work, we examine the SO and SO$_2$ emission that is detected from four sources: DG Tau, HL Tau, IRAS 04302+2247, and T Tau. The comparison with CO, HCO$^+$, and CS maps reveals that the SO and SO$_2$ emission originates at the intersection between extended streamers and the planet-forming disk. Two targets, DG Tau and HL Tau, offers clear cases of inflowing material inducing an accretion shock on the disk material. The measured rotational temperatures and radial velocities are consistent with this view. In contrast to younger Class 0 sources, these shocks are confined to the specific disk region impacted by the streamer. In HL Tau, the known accreting streamer induces a shock in the disk outskirt, and the released SO and SO$_2$ molecules spiral toward the star in a few hundreds years. These results suggest that shocks induced by late accreting material may be common in the disks of young star-forming regions with possible consequences on the chemical composition and mass content of the disk. They also highlight the importance of SO and SO$_2$ line observations to probe accretion shocks from a larger sample.