A magnetically driven disc wind in the inner disc of PDS 70

TL;DR

This study detects a magnetically driven disc wind in PDS 70's inner disc, suggesting it may significantly influence disc evolution alongside planetary clearing, with implications for understanding planet formation environments.

Contribution

First detection of a magnetically driven disc wind in PDS 70's inner disc, highlighting its potential role in disc clearing alongside planetary influences.

Findings

Detection of [O I] 6300AA line indicating wind presence

High [O I] luminosity relative to accretion luminosity

Wind emission and variability in He I 10830AA line

Abstract

PDS 70 is so far the only young disc where multiple planets have been detected by direct imaging. The disc has a large cavity when seen at sub-mm and NIR wavelengths, which hosts two massive planets. This makes PDS 70 the ideal target to study the physical conditions in a strongly depleted inner disc shaped by two giant planets, and in particular to test whether disc 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] 6300AA 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 discs with cavities in nearby star-forming regions. The FWHM and blue-shifted peak of the [O I] line suggest an emission in a region very close to the star, favouring a magnetically driven wind as the origin. We also detect wind emission and high variability in the He I 10830AA 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 disc wind could also have had a significant contribution to clearing the inner-disc.