The Observational Anatomy of Externally Photoevaporating Planet-Forming Discs I: Atomic Carbon

Abstract

We demonstrate the utility of CI as a tracer of photoevaporative winds that are being driven from discs by their ambient UV environment. Commonly observed CO lines only trace these winds in relatively weak UV environments and are otherwise dissociated in the wind at the intermediate to high UV fields that most young stars experience. However, CI traces unsubtle kinematic signatures of a wind in intermediate UV environments ($\sim 1000$G${}_0$) and can be used to place constraints on the kinematics and temperature of the wind. In CI position-velocity diagrams external photoevaporation results in velocities that are faster than those from Keplerian rotation alone, as well as emission from quadrants of position-velocity space in which there would be no Keplerian emission. This is independent of viewing angle because the wind has components that are perpendicular to the azimuthal rotation of the disc. At intermediate viewing angles ($\sim 30-60^{\circ }$) moment 1 maps also exhibit a twisted morphology over large scales (unlike other processes that result in twists, which are typically towards the inner disc). CI is readily observable with ALMA, which means that it is now possible to identify and characterise the effect of external photoevaporation on planet-forming discs in intermediate UV environments.

12 pages, accepted for publication in MNRAS

References in corpus (11)

• Early Science with SOFIA, the Stratospheric Observatory for Infrared Astronomy
• Meridional flows in the disk around a young star
• Direct mapping of the temperature and velocity gradients in discs. Imaging the vertical CO snow line around IM Lupi
• The Photoevaporation of Discs Around Young Stars in Massive Clusters
• ALMA Observations of the Orion Proplyds
• UV Radiation Fields Produced by Young Embedded Star Clusters
• Planet population synthesis driven by pebble accretion in cluster environments
• Proplyds around a B1 star - 42 Orionis in NGC 1977
• The first multi-dimensional view of mass loss from externally FUV irradiated protoplanetary discs
• Photochemical-dynamical models of externally FUV irradiated protoplanetary discs
• 3D shape of Orion A with Gaia DR2. An informed view on Star Formation Rates and Efficiencies

Cited by in corpus (16)

• Global Hydromagnetic Simulations of Protoplanetary Disks with Stellar Irradiation and Simplified Thermochemistry
• Large-scale CO spiral arms and complex kinematics associated with the T Tauri star RU Lup
• Proplyds in the Flame Nebula NGC 2024
• An ALMA survey of $\lambda$ Orionis disks: from supernovae to planet formation
• Effects of stellar density on the photoevaporation of circumstellar discs
• Molecular Mapping of DR Tau's Protoplanetary Disk, Envelope, Outflow, and Large-Scale Spiral Arm
• Testing viscous disc theory using the balance between stellar accretion and external photoevaporation of protoplanetary discs
• [OI] 6300Å emission as a probe of external photoevaporation of protoplanetary discs
• PDRs4All. X. ALMA and JWST detection of neutral carbon in the externally irradiated disk d203-506: Undepleted gas-phase carbon
• Rapid CO gas dispersal from NO Lup's class III circumstellar disc
• A slim disc approach to external photoevaporation of discs
• An APEX search for carbon emission from NGC 1977 proplyds
• Searching for wide-orbit gravitational instability protoplanets with ALMA in the dust continuum
• Debris Disks
• H3+ in irradiated protoplanetary disks: Linking far-ultraviolet radiation and water vapor
• Line ratio identification of external photoevaporation