Sulphur monoxide emission tracing an embedded planet in the HD 100546 protoplanetary disk

Abstract

Molecular line observations are powerful tracers of the physical and chemical conditions across the different evolutionary stages of star, disk, and planet formation. The high angular resolution and unprecedented sensitivity of the Atacama Large Millimeter Array (ALMA) enables the current drive to detect small-scale gas structures in protoplanetary disks that can be attributed directly to forming planets. We report high angular resolution ALMA Band 7 observations of sulphur monoxide (SO) in the nearby planet-hosting disk around the Herbig star HD 100546. SO is rarely detected in evolved protoplanetary disks, but in other environments, it is most often used as a tracer of shocks. The SO emission from the HD 100546 disk primarily originates from gas within the ≈20 au millimeterdust cavity and shows a clear azimuthal brightness asymmetry of a factor of 2. In addition, the difference in the line profile shape is significant when these new Cycle 7 data are compared to Cycle 0 data of the same SO transitions. We discuss the different physical and chemical mechanisms that might cause this asymmetry and time variability, including disk winds, disk warps, and a shock triggered by a (forming) planet. We propose that SO is enhanced in the cavity by the presence of a giant planet. The SO asymmetry complements evidence for hot circumplanetary material around giant planet HD 100546 c that is traced via CO ro-vibrational emission. This work sets the stage for further observational and modelling efforts to detect and understand the chemical imprint of a forming planet on its parent disk.

An SMA Survey of Chemistry in Disks Around Herbig AeBe Stars

“…Otherwise, Oph IRS 48 has been detected in a mix of commonly and uncommonly targeted molecules, including H 2 CO, CH 3 OH, NO, SO, SO 2 , and CH 3 OCH 3 (van der Marel et al 2014;Booth et al 2021;van der Marel et al 2021;Brunken et al 2022). Other molecule-specific exceptions include DCO + from HD 169142 (Macías et al 2017), H 2 CO, CH 3 OH, and SO from HD 100546 (Booth et al 2018(Booth et al , 2023, HC 15 N and H 13 CO + from HD 97048 (Booth et al 2019), and upper limits of CN, H 2 CO, and SO from HD 36112 (also known as MWC 758; Guilloteau et al 2013).…”

Early Planet Formation in Embedded Disks (eDisk). IV. The Ringed and Warped Structure of the Disk around the Class I Protostar L1489 IRS

“…While bright, compact SO emission is detected in the innermost region, a CH 3 OH transition with an upper state energy of 45 K, which is observed in the same spectral setup, is not detected. In the Class II disks around IRS 48 and HD 100546, SO emission and bright emission from complex organic molecules including CH 3 OH has been detected cospatially (Booth et al 2021a(Booth et al , 2021bBrunken et al 2022;Booth et al 2023), indicating a hot-corino-like chemistry in the warm (100 K) region. The detection of SO and the nondetection of CH 3 OH in the L1489 IRS disk may indicate that the temperature is not high enough for CH 3 OH ice to thermally sublimate: while the sublimation temperature of SO is ∼50 K (e.g., Sakai et al 2014;Aota et al 2015;Miura et al 2017), a higher temperature (∼100 K) is required for CH 3 OH ice to sublimate.…”

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

“…Given that DR Tau is now known to be partially embedded, its asymmetric SO emission may arise in a manner similar to Class I systems. Booth et al (2023) proposed that an SO asymmetry in the HD 100546 disk could be due to shocks from gas accreting onto an embedded planet. This likely does not account for DR Tau's SO asymmetry, since highcontrast imaging from Mesa et al (2022) rules out the presence of a companion above several Jupiter masses at separations greater than 50 au from DR Tau.…”