A Magnetically Driven Disk Wind in the Inner Disk of PDS 70*

Abstract

PDS 70 is so far the only young disk where multiple planets have been detected by direct imaging. The disk has a large cavity when seen at submillimeter and near-infrared wavelengths, which hosts two massive planets. This makes PDS 70 the ideal target to study the physical conditions in a strongly depleted inner disk shaped by two giant planets, and in particular to test whether disk winds can play a significant role in its evolution. Using X-Shooter and HARPS spectra, we detected for the first time the wind-tracing [O i] 6300 Å line, and confirm the low-moderate value of mass-accretion rate in the literature. The [O i] line luminosity is high with respect to the accretion luminosity when compared to a large sample of disks with cavities in nearby star-forming regions. The FWHM and blueshifted peak of the [O i] line suggest an emission in a region very close to the star, favoring a magnetically driven wind as the origin. We also detect wind emission and high variability in the He i 10830 Å line, which is unusual for low accretors. We discuss that, although the cavity of PDS 70 was clearly carved out by the giant planets, the substantial inner-disk wind could also have had a significant contribution to clearing the inner disk.

The Dynamic, Chimeric Inner Disk of PDS 70

“…Variable, blueshifted (−35 to −110 km s −1 ) and redshifted (∼140 km s −1 ) absorption components are seen in He I spectra of PDS 70 obtained at three epochs prior to MJD = 58900 (Thanathibodee et al 2020(Thanathibodee et al , 2022, indicative of magnetospheric accretion. After MJD = 58900, when the photometric behavior has transitioned from a periodic to aperiodic dipper-like behavior, He I spectra at two separate epochs at the end of 2020/early 2021 lack any redshifted absorption and instead have redshifted emission and strong blueshifted absorption, suggestive of a disk wind (Campbell-White et al 2023). This is also coincident with a decrease in the baseline stellar brightness and a rise in infrared emission (Figure 6).…”

“…Although Balmer Hα and X-ray emissions from the star lie within the range of nonaccreting weak-lined T Tauri stars (Joyce et al 2020) and far-UV continuum emission from accretion shocks is absent (Skinner & Audard 2022), the reversed profile of the Hα line and fluorescent H 2 emission point to primordial disk gas and low-level (10 −10 M e yr −1 ) accretion (Thanathibodee et al 2020;Skinner & Audard 2022). Absorption in the 1.083 μm He I triplet and emission in the forbidden [O I] 6300 Å line (Campbell-White et al 2023) reveal a wind that could drive this accretion (Thanathibodee et al 2020).…”

JWST MIRI MRS Images of Disk Winds, Water, and CO in an Edge-on Protoplanetary Disk

“…Although MHD wind models can successfully reproduce the decline in M acc  and M disk over time, an unambiguous distinction between outflow-launching mechanisms in the inner disk remains elusive (jets, MHD, and photoevaporative winds; see, e.g., Pascucci et al 2023 for a recent review). Outflow signatures are readily identified in high-resolution spectroscopy, which reveals blueshifted emission and absorption lines from atomic transitions, including [O I], [Ne II], [N II], [S II], He I, and C II (Edwards et al 1987;Kwan & Tademaru 1995;Pascucci & Sterzik 2009;Fang et al 2018Fang et al , 2023aBanzatti et al 2019;Haffert et al 2020;Xu et al 2021;Campbell-White et al 2023). The central velocities and FWHM of the line profiles, which can be interpreted as average outflow velocities and radial locations within a Keplerian disk, are typically used to distinguish between an origin in photoevaporative and/or MHD winds.…”

“…The central velocities and FWHM of the line profiles, which can be interpreted as average outflow velocities and radial locations within a Keplerian disk, are typically used to distinguish between an origin in photoevaporative and/or MHD winds. For example, a more compact emitting region (r ∼ 0.1-0.2 au) is assumed to be characteristic of an MHD wind (Campbell-White et al 2023). Particularly the line flux ratios of [Ne II] 12.814 μm and [O I] 6300 Å in low-velocity photoevaporative winds increase as emission from the warm inner disk dust declines (Pascucci et al 2020).…”