ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT)

VI. Accretion shocks in the disk of DG Tau and HL Tau^★

¹ INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
e-mail: antonio.garufi@inaf.it
² Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38000 Grenoble, France
³ Center for Astrochemical Studies, Max Planck Institute for Extraterrestrial Physics, Garching 85748, Germany
⁴ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
⁵ Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Via G. Sansone 1, 50019 Sesto Fiorentino, Italy
⁶ Joint ALMA Observatory, Av. Alonso de Cordova 3107, Vitacura, Santiago, Chile

Received: 7 May 2021
Accepted: 27 October 2021

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 SO₂ 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 SO₂ emission originates at the intersection between extended streamers and the planet-forming disk. Two targets, DG Tau and HL Tau, offer 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 outskirts, and the released SO and SO₂ molecules spiral toward the star in a few hundred 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 for the chemical composition and mass content of the disk. They also highlight the importance of SO and SO₂ line observations in probing accretion shocks from a larger sample.