Title: Dust-trapping vortices and a potentially planet-triggered spiral wake in the pre-transitional disk of V1247 Orionis,
Abstract: The radial drift problem constitutes one of the most fundamental problems in
planet formation theory, as it predicts particles to drift into the star before
they are able to grow to planetesimal size. Dust-trapping vortices have been
proposed as a possible solution to this problem, as they might be able to trap
particles over millions of years, allowing them to grow beyond the radial drift
barrier. Here, we present ALMA 0.04"-resolution imaging of the pre-transitional
disk of V1247 Orionis that reveals an asymmetric ring as well as a
sharply-confined crescent structure, resembling morphologies seen in
theoretical models of vortex formation. The asymmetric ring (at 0.17"=54 au
separation from the star) and the crescent (at 0.38"=120 au) seem smoothly
connected through a one-armed spiral arm structure that has been found
previously in scattered light. We propose a physical scenario with a planet
orbiting at $\sim0.3$"$\approx$100 au, where the one-armed spiral arm detected
in polarised light traces the accretion stream feeding the protoplanet. The
dynamical influence of the planet clears the gap between the ring and the
crescent and triggers two vortices that trap mm-sized particles, namely the
crescent and the bright asymmetry seen in the ring. We conducted dedicated
hydrodynamics simulations of a disk with an embedded planet, which results in
similar spiral-arm morphologies as seen in our scattered light images. At the
position of the spiral wake and the crescent we also observe $^{12}$CO (3-2)
and H$^{12}$CO$^{+}$ (4-3) excess line emission, likely tracing the increased
scale-height in these disk regions.