Analysis of the arm-like structure in the outer disk of PDS 70. Spiral density wave or vortex?

Abstract

Observing dynamical interactions between planets and disks is key to understanding their formation and evolution. Two protoplanets have recently been discovered within PDS 70's protoplanetary disk, along with an arm-like structure towards the north-west of the star. Our aim is to constrain the morphology and origin of this arm-like structure, and to assess whether it could trace a spiral density wave caused by the dynamical interaction between the planet PDS 70c and the disk. We analyze polarized and angular differential imaging (PDI and ADI) data taken with VLT/SPHERE, spanning six years of observations. PDI data sets are reduced using the IRDAP polarimetric data reduction pipeline, while ADI data sets are processed using MUSTARD, a novel inverse problem algorithm to tackle the geometrical biases spoiling the images previously used for the analysis of this disk. We confirm the presence of the arm-like structure in all PDI and ADI datasets. We do not observe a south-east symmetric arm with respect to the disk minor axis, which seems to disfavor the previous hypothesis that the arm is the footprint of a double-ring structure. If the structure traces a spiral density wave following the motion of PDS 70c, we would expect $11\stackrel{\circ }{.}28_{-0\stackrel{\circ }{.}86}^{+2\stackrel{\circ }{.}20}$ rotation for the spiral in six years. However, we do not measure any significant movement of the structure. If the arm-like structure is a planet-driven spiral arm, the observed lack of rotation would suggest that the assumption of rigid-body rotation may be inappropriate for spirals induced by planets. We suggest that the arm-like structure may rather trace a vortex appearing as a one-armed spiral in scattered light due to projection effects. The vortex hypothesis accounts for both the lack of observed rotation and the presence of a nearby sub-mm continuum asymmetry detected with ALMA.

Accepted for publication in Astronomy&Astrophysics. 11 pages, 10 figures

References in corpus (26)

• The Gaia mission
• Two accreting protoplanets around the young star PDS 70
• Monte Carlo radiative transfer in protoplanetary disks
• A Circumplanetary Disk Around PDS70c
• VIP: Vortex Image Processing package for high-contrast direct imaging
• Submillimeter emission associated with candidate protoplanets
• Highly structured disk around the planet host PDS 70 revealed by high-angular resolution observations with ALMA
• Constraining the Nature of the PDS 70 Protoplanets with VLTI/GRAVITY
• The polarimetric imaging mode of VLT/SPHERE/IRDIS II: Characterization and correction of instrumental polarization effects
• VLT/SPHERE exploration of the young multiplanetary system PDS70
• Flybys in protoplanetary discs: II. Observational signatures
• A survey of the linear polarization of directly imaged exoplanets and brown dwarf companions with SPHERE-IRDIS. First polarimetric detections revealing disks around DH Tau B and GSC 6214-210 B
• Ongoing flyby in the young multiple system UX Tauri
• Separating extended disc features from the protoplanet in PDS 70 using VLT/SINFONI
• Scattered light mapping of protoplanetary disks
• The theory of kinks -- I. A semi-analytic model of velocity perturbations due to planet-disc interaction
• Are the spiral arms in the MWC 758 protoplanetary disc driven by a companion inside the cavity?
• Dynamical Evidence of a Spiral Arm--Driving Planet in the MWC 758 Protoplanetary Disk
• Vortex-like kinematic signal, spirals, and beam smearing effect in the HD 142527 disk
• REXPACO: an algorithm for high contrast reconstruction of the circumstellar environment by angular differential imaging
• Spiral Arm Pattern Motion in the SAO 206462 Protoplanetary Disk
• Dust traps as planetary birthsites: basics and vortex formation
• A faint companion around CrA-9: protoplanet or obscured binary?
• The Appearance of Vortices in Protoplanetary Disks in Near-Infrared Scattered Light
• Self-Sustaining Vortices in Protoplanetary Disks: Setting the Stage for Planetary System Formation
• Search for Stellar Flybys in the Sco-Cen OB Association with the Gaia DR2

Cited by in corpus (9)

• Protoplanetary disks in $K_s$-band total intensity and polarized light
• WIde Separation Planets In Time (WISPIT): A Gap-clearing Planet in a Multi-ringed Disk around the Young Solar-type Star WISPIT 2
• MINDS: JWST/NIRCam imaging of the protoplanetary disk PDS 70
• Apocenter pile-up and arcs: a narrow dust ring around HD 129590
• PDS 70 unveiled by star-hopping: total intensity, polarimetry and mm-imaging modeled in concert
• Inverse-problem versus principal component analysis methods for angular differential imaging of circumstellar disks. The mustard algorithm
• Combining reference-star and angular differential imaging for high-contrast imaging of extended sources
• Karhunen-Loève Data Imputation in High Contrast Imaging
• Keplerian motion of a compact source orbiting the inner disc of PDS 70: a third protoplanet in resonance with b and c?