Variable structure in the PDS70 disc and uncertainties in radio-interferometric image restoration

Abstract

The compact mm-wavelength signal in the central cavity of the PDS70 disc, revealed by deep ALMA observations, is aligned with unresolved Halpha emission, and is thought to stem from a circum-planetary disc (CPD) around PDS70c. We revisit the available ALMA data on PDS70c with alternative imaging strategies, and with special attention to uncertainties and to the impact of the so-called "JvM correction", which is thought to improve the dynamic range of restored images. We also propose a procedure for the alignment and joint imaging of multi-epoch visibility data. We find that the JvM correction exaggerates the peak signal-to-noise of the data, by up to a factor of 10. In the case of PDS70, we recover the detection of PDS70c from the July 2019 data, but only at 8sigma. However, its non-detection in Dec. 2017 suggests that PDS70c is variable by at least 42%+-13% over a 1.75yr time-span, so similar to models of the Halpha variability. We also pick up fine structure in the inner disc, such that its peak is offset by ~ 0.04" from the disc centre. The inner disc is variable too, which we tentatively ascribe to Keplerian rotation as well as intrinsic morphological changes.

arXiv commentaccepted MNRAS

References in corpus (29)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• A multi-scale multi-frequency deconvolution algorithm for synthesis imaging in radio interferometry
• Two accreting protoplanets around the young star PDS 70
• Molecules with ALMA at Planet-forming Scales (MAPS) I: Program Overview and Highlights
• The Anisotropy of the Microwave Background to l = 3500: Mosaic Observations with the Cosmic Background Imager
• Compressed sensing imaging techniques for radio interferometry
• A Circumplanetary Disk Around PDS70c
• Interferometric Imaging Directly with Closure Phases and Closure Amplitudes
• Submillimeter emission associated with candidate protoplanets
• Highly structured disk around the planet host PDS 70 revealed by high-angular resolution observations with ALMA
• Accretion kinematics through the warped transition disk in HD142527 from resolved CO(6-5) observations
• Morphological analysis of the cm-wave continuum in the dark cloud LDN1622
• An inner warp in the DoAr 44 T Tauri transition disk
• Separating extended disc features from the protoplanet in PDS 70 using VLT/SINFONI
• Differences in the gas and dust distribution in the transitional disk of a sun-like young star, PDS 70
• A dusty filament and turbulent CO spirals in HD135344B-SAO206462
• Limits on Millimeter Continuum Emission from Circumplanetary Material in the DSHARP Disks
• On the accuracy of the ALMA flux calibration in the time domain and across spectral windows
• Observability of Forming Planets and their Circumplanetary Disks I. -- Parameter Study for ALMA
• Hydrogen recombination line luminosities and -variability from forming planets
• Multi-GPU maximum entropy image synthesis for radio astronomy
• Cm-wavelength observations of MWC758: resolved dust trapping in a vortex
• Optimal Image Reconstruction in Radio Interferometry
• Cooling in the shade of warped transition disks
• High-Resolution Near Infrared Spectroscopy of HD~100546: IV. Orbiting Companion Disappears on Schedule
• Self-consistent modelling of the dust component in protoplanetary and circumplanetary disks: the case of PDS 70
• Resolved spectral variations of the centimetre-wavelength continuum from the rho Oph W photo-dissociation-region
• Bayesian Image Reconstruction Based on Voronoi Diagrams