Molecular Mapping of DR Tau's Protoplanetary Disk, Envelope, Outflow, and Large-scale Spiral Arm

DR Tau has been noted for its unusually high variability in comparison with other T Tauri stars. Although it is one of the most extensively studied pre-main-sequence stars, observations with millimeter interferometry have so far been relatively limited. We present NOEMA images of (CO)-C-12, (CO)-C-13, (CO)-O-18, SO, DCO+, and H2CO toward DR Tau at a resolution of similar to 0.'' 5 (similar to 100 au). In addition to the protoplanetary disk, CO emission reveals an envelope, a faint asymmetric outflow, and a spiral arm with a clump. The similar to 1200 au extent of the CO arm far exceeds that of the spiral arms previously detected in scattered light, which underlines the necessity of sensitive molecular imaging for contextualizing the disk environment. The kinematics and compact emission distribution of (CO)-O-18, SO, DCO+, and H2CO indicate that they originate primarily from within the Keplerian circumstellar disk. The SO emission, though, also exhibits an asymmetry that may be due to interaction with infalling material or unresolved substructure. The complex environment of DR Tau is reminiscent of those of outbursting FUor sources and some EXor sources, suggesting that DR Tau's extreme stellar activity could likewise be linked to disk instabilities promoted by large-scale infall.