High-resolution [O I] line spectral mapping of TW Hya supportive of a magnetothermal wind

Abstract

Disk winds are thought to play a critical role in the evolution and dispersal of protoplanetary disks. A primary diagnostic of this physics is emission from the wind, especially in the low-velocity component of the [O I] λ6,300 line. However, the interpretation of the line is usually based on spectroscopy alone, which leads to confusion between magnetohydrodynamic winds and photoevaporative winds. Here we report that in high-resolution spectral mapping of TW Hya by the multi-unit spectroscopic explorer at the Very Large Telescope, 80% of the [O I] emission is confined to within 1 au radially from the star. A generic model of a magnetothermal wind produces [O I] emission at the base of the wind that broadly matches the flux and the observed spatial and spectral profiles. The emission at large radii is much fainter than predicted from models of photoevaporation, perhaps because the magnetothermal wind partially shields the outer disk from energetic radiation from the central star. This result calls into question the previously assessed importance of photoevaporation in disk dispersal predicted by models.