The Doppler-flip in HD100546 as a disk eruption: the elephant in the room of kinematic protoplanet searches

TL;DR

This study reinterprets a prominent Doppler flip in HD100546's disk as a disk eruption caused by a surface disturbance, challenging the planet-induced origin hypothesis and highlighting the complexity of kinematic signals.

Contribution

It introduces a new interpretation of the Doppler flip as a disk eruption driven by a small embedded body, contrasting with the common planet-detection approach.

Findings

Doppler flip caused by vertical motions, not a planet.

Disk rotation consistent with a 2.1-2.3 solar mass star.

Proposed disk eruption driven by a ~10 Earth-mass body.

Abstract

The interpretation of molecular-line data in terms of hydro dynamical simulations of planet-disk interactions fosters new hopes for the indirect detection of protoplanets. In a model-independent approach, embedded protoplanets should be found at the roots of abrupt Doppler flips in velocity centroid maps. However, the largest velocity perturbation known for an unwarped disk, in the disk of HD100546, leads to a conspicuous Doppler flip that coincides with a thick dust ring, in contradiction with an interpretation in terms of a >~ 1Mjup body. Here we present new ALMA observations of the 12CO(2-1) kinematics in HD\,100546, with a factor of two finer angular resolutions. We find that the disk rotation curve is consistent with a central mass 2.1 < M* /Msun < 2.3, and that the blue-shifted side of the Doppler flip is due to vertical motions, reminiscent of the disk wind proposed previously from blue-shifted SO lines. We tentatively propose a qualitative interpretation in terms of a surface disturbance to the Keplerian flow, i.e. a disk eruption, driven by an embedded outflow launched by a ~10Mearth body. Another interpretation involves a disk-mass-loading hot-spot at the convergence of an envelope accretion streamer.