Results of the summarizing process for the arXiv paper: 2210.14820v1

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.

• 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.

Unveiling the Chemical Imprint of a Forming Planet on its Parent Protoplanetary Disk with ALMA

Background: Protoplanetary Disks and Molecular Line Observations

Protoplanetary disks are circumstellar discs made up of gas and dust that surround young stars. They are believed to be sites where planets form through gravitational collapse or core accretion processes. Molecular line observations are powerful tracers of the physical and chemical conditions across these different evolutionary stages as they allow us to detect small-scale gas structures that may indicate planetary formation within protoplanetary disks.

Sulphur monoxide (SO) is rarely detected in evolved protoplanetary disks but is often used as a tracer of shocks in other environments such as outflows or jets associated with young stellar objects (YSOs). It has been observed at millimetre wavelengths by single dish telescopes towards several YSOs including Class I sources, transitional disks, and Herbig Ae/Be stars like HD 100546. However, due to limited spatial resolution it was not possible to identify any small-scale structures associated with forming planets until now thanks to ALMA's unprecedented capabilities for imaging at millimetre wavelengths with high angular resolution (~0\farcs1).

Observations & Results: Azimuthal Brightness Asymmetry Detected Around HD 100546

High angular resolution ALMA Band 7 observations of SO were conducted in the nearby planet-hosting disk around Herbig star HD 100546 using both Cycle 0 and Cycle 7 data sets. The authors report a clear azimuthal brightness asymmetry between these two datasets which could be attributed directly to forming planets within the disk cavity (~20 au mm-dust cavity). The SO emission primarily originates from gas within this cavity and shows a factor two difference in brightness when comparing Cycle 0 vs Cycle 7 data sets indicating time variability which could also be linked back to planetary formation processes occurring within this region over time.

Discussion & Conclusion: Evidence for Hot Circumplanetary Material Traced via CO Ro-Vibrational Emission

The authors discuss various physical/chemical mechanisms that could be responsible for this asymmetry such as disk winds, warps or shocks triggered by a forming giant planet inside the cavity which would enhance SO emission due its presence there compared to outside regions further away from it where no such enhancement would occur if only wind/warp related effects were present instead.. This hypothesis is supported by evidence for hot circumplanetary material around the giant planet HD 100546 c traced via CO ro-vibrational emission suggesting that shock heating may indeed play an important role here too..

Overall, this work 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 before they become detectable through direct imaging techniques. This study sets the stage for further observational efforts combined with modeling efforts aimed at detecting more detailed information about these processes taking place inside protoplanetary disks during early phases of planetary evolution.