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

**Authors:** Alice S. Booth, John D. Ilee, Catherine Walsh, Mihkel Kama, Luke Keyte, Ewine F. van Dishoeck, Hideko Nomura  
**arXiv:** [2210.14820](https://arxiv.org/abs/2210.14820)  
**Date:** 2022-10-26  
**Summary page:** https://www.summarizepaper.com/en/paper/2210.14820v1/

## Key points

- The Atacama Large Millimeter Array (ALMA) has enabled the detection of small-scale gas structures in protoplanetary disks that can be attributed directly to forming planets.
- High angular resolution ALMA Band 7 observations of sulphur monoxide (SO) were conducted in the nearby planet-hosting disk around Herbig star HD 100546.
- The SO emission from the HD 100546 disk primarily originates from gas within the approximately 20 au mm-dust cavity and shows a clear azimuthal brightness asymmetry of a factor two.
- There is a significant difference in the line profile shape when comparing new Cycle 7 data to Cycle 0 data of the same SO transitions, which could be due to various physical/chemical mechanisms such as disk winds, disk warps, or a shock triggered by a (forming) planet.
- The authors propose that the SO is enhanced in the cavity due to the presence of a giant planet, which complements evidence for hot circumplanetary material around the giant planet HD 100546 c traced via CO ro-vibrational emission.
- This study highlights how molecular line observations with ALMA can provide valuable insights into protoplanetary disks' physical and chemical properties during different evolutionary stages leading up to planet formation.

## Summary

The Atacama Large Millimeter Array (ALMA) has enabled the detection of small-scale gas structures in protoplanetary disks that can be attributed directly to forming planets. Molecular line observations are powerful tracers of the physical and chemical conditions across the different evolutionary stages of star, disk, and planet formation. In this study, high angular resolution ALMA Band 7 observations of sulphur monoxide (SO) were conducted in the nearby planet-hosting disk around Herbig star HD 100546. SO is rarely detected in evolved protoplanetary disks but is often used as a tracer of shocks in other environments. The SO emission from the HD 100546 disk primarily originates from gas within the approximately 20 au mm-dust cavity and shows a clear azimuthal brightness asymmetry of a factor two. The authors report a significant difference in the line profile shape when comparing these new Cycle 7 data to Cycle 0 data of the same SO transitions. They discuss various physical/chemical mechanisms that could be responsible for this asymmetry and time variability, including disk winds, disk warps, and a shock triggered by a (forming) planet. The authors propose that the SO is enhanced in the cavity due to the presence of a giant planet. The SO asymmetry complements evidence for hot circumplanetary material around the giant planet HD 100546 c traced via CO ro-vibrational emission. This work sets the stage for further observational and modeling efforts to detect and understand the chemical imprint of a forming planet on its parent disk. Overall, this study highlights how molecular line observations with ALMA can provide valuable insights into protoplanetary disks' physical and chemical properties during different evolutionary stages leading up to planet formation. It demonstrates how ALMA can be used to detect signatures associated with forming planets such as azimuthal brightness asymmetries or time variability which may indicate their presence in protoplanetary disks before they become detectable through direct imaging techniques.