Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Late infall causing disk warp and gravitational instability in SU Aur∗

SU Aur is one of the targets of the DESTINYS ESO large program, in which we study the evolution of gas-rich circumstellar disks within the first 10 Myr with near-infrared scattered light imaging. We are in particular interested in the presence of sub-structures in the disk, as well as the presence of forming planets and how the two may be linked. We used VLT/SPHERE in polarimetric imaging mode in the near infrared to spatially resolve the disk around SUAur down to scales of ∼ 7au. In addition to the new SPHERE observations we utilize VLT/NACO, HST/STIS and ALMA archival data. The new SPHERE data shows the disk around SU Aur as well as extended dust structures in unprece- dented detail. We resolve for the first time several dust tails connected to the Keplerian disk. By comparison with ALMA data we show that these dust tails are caused by material falling onto the disk. The disk itself shows an intricate spiral structure, consistent with gravitational instability, as well as a shadow lane, cast by an inner, misaligned component. Our observations suggest that SUAur is undergoing late infall of material, which can explain the observed disk structures. SU Aur, along with AB Aur are the clearest observational examples of this mechanism at work. The resulting warping of the disk may well explain the spin-orbit misalignment observed for many detected exoplanet systems.