Constraints on photoevaporation models from (lack of) radio emission in the Corona Australis protoplanetary disks

Abstract

Photoevaporation due to high-energy stellar photons is thought to be one of the main drivers of protoplanetary disk dispersal. The fully or partially ionized disk surface is expected to produce free-free continuum emission at centimeter (cm) wavelengths that can be routinely detected with interferometers such as the upgraded Very Large Array (VLA). We use deep (rms noise down to 8 $\mu$Jy beam${}^{-1}$ in the field of view center) 3.5 cm maps of the nearby (130 pc) Corona Australis (CrA) star formation (SF) region to constrain disk photoevaporation models. We find that the radio emission from disk sources in CrA is surprisingly faint. Only 3 out of 10 sources within the field of view are detected, with flux densities of order $10^2$ $\mu$Jy. However, a significant fraction of their emission is non-thermal. Typical upper limits for non-detections are $3\sigma \sim 60\mu$Jy beam${}^{-1}$. Assuming analytic expressions for the free-free emission from extreme-UV (EUV) irradiation, we derive stringent upper limits to the ionizing photon luminosity impinging on the disk surface ${\Phi }_{\mathrm{EUV}}<1-4\times 10^{41}$ s${}^{-1}$. These limits constrain ${\Phi }_{\mathrm{EUV}}$ to the low end of the values needed by EUV-driven photoevaporation models to clear protoplanetary disks in the observed few Myr timescale. Therefore, at least in CrA, EUV-driven photoevaporation is not likely to be the main agent of disk dispersal. We also compare the observed X-ray luminosities $L_X$ of disk sources with models in which photoevaporation is driven by such photons. Although predictions are less specific than for the EUV case, most of the observed fluxes (upper limits) are roughly consistent with the (scaled) predictions. Deeper observations, as well as predictions spanning a wider parameter space, are needed to properly test X-ray driven photoevaporation.

arXiv commentAccepted as a Letter in Astronomy & Astrophysics

References in corpus (25)

• Spitzer Space Telescope study of disks in the young $\sigma$ Orionis cluster
• Photoevaporation of protoplanetary discs II: evolutionary models and observable properties
• Dust Properties of Protoplanetary Disks in the Taurus-Auriga Star Forming Region from Millimeter Wavelengths
• Photoevaporation of Circumstellar Disks by FUV, EUV and X-ray Radiation from the Central Star
• Radiation-Hydrodynamic Models of X-Ray & EUV Photoevaporating Protoplanetary Discs
• ISO spectroscopy of disks around Herbig Ae/Be stars
• Photoevaporation of Circumstellar Disks around Young Stars
• Large dust particles in disks around T Tauri stars
• Giant planet migration, disk evolution, and the origin of transitional disks
• Towards Planetesimals in the Disk around TW Hya: 3.5 centimeter Dust Emission
• Evidence for Disk Photoevaporation Driven by the Central Star
• Diagnostic Line Emission from EUV and X-ray Illuminated Disks and Shocks around Low Mass stars
• The Transitional Protoplanetary Disk Frequency as a Function of Age: Disk Evolution in the Coronet Cluster, Taurus, and Other 1--8 Myr-old Regions
• The Spitzer Survey of Interstellar Clouds in the Gould Belt. III. A Multi-Wavelength View of Corona Australis
• Constraints on the ionizing flux emitted by T Tauri stars
• Free-free Emission and Radio Recombination Lines from Photoevaporating Disks
• ALMA observations of the kinematics and chemistry of disc formation
• Low EUV Luminosities Impinging on Protoplanetary Disks
• Coronae in the Coronet: A very deep X-ray look into a stellar nursery
• Protostars, multiplicity, and disk evolution in the Corona Australis region: A Herschel Gould Belt Study
• Time Monitoring of Radio Jets and Magnetospheres in the Nearby Young Stellar Cluster R Coronae Australis
• Simultaneous X-ray, radio, near-infrared, and optical monitoring of Young Stellar Objects in the Coronet cluster
• The very low-mass population of the Corona Australis and Chamaeleon II star forming regions
• Centimeter Imaging of the R Coronae Australis Region
• Testing protoplanetary disc dispersal with radio emission

Cited by in corpus (10)

• The anomalously low (sub)millimeter spectral indices of some protoplanetary disks may be explained by dust self-scattering
• ALMA survey of Class II protoplanetary disks in Corona Australis: a young region with low disk masses
• Disk Dispersal: Theoretical Understanding and Observational Constraints
• Imaging the photoevaporating disk and radio jet of GM Aur
• A concordant scenario to explain FU Ori from deep centimeter and millimeter interferometric observations
• A WISE-based search for debris discs amongst M-dwarfs in nearby, young, moving groups
• VLA cm-wave survey of young stellar objects in the Oph A cluster: constraining extreme UV- and X-ray-driven disk photo-evaporation -- A pathfinder for Square Kilometre Array studies
• The centimeter emission from planet-forming disks in Taurus
• Absence of Significant Cool Disks in Young Stellar Objects Exhibiting Repetitive Optical Outbursts
• A Dual-Band Centimetre Continuum Monitoring Survey of Young Stellar Objects in the Coronet Cluster