Distributions of gas and small and large grains in the LkHα 330 disk trace a young planetary system,

Abstract

Planets that are forming around young stars are expected to leave clear imprints in the distribution of the gas and dust of their parental protoplanetary disks. In this paper, we present new scattered light and millimeter observations of the protoplanetary disk around LkHα 330, using SPHERE/VLT and ALMA, respectively. The scattered-light SPHERE observations reveal an asymmetric ring at around 45 au from the star in addition to two spiral arms with similar radial launching points at around 90 au. The millimeter observations from ALMA (resolution of 0.06″ × 0.04″) mainly show an asymmetric ring located at 110 au from the star. In addition to this asymmetry, there are two faint symmetric rings at 60 au and 200 au. The 12CO, 13CO, and C18O lines seem to be less abundant in the inner disk (these observations have a resolution of 0.16″ × 0.11″). The 13CO peaks at a location similar to the inner ring observed with SPHERE, suggesting that this line is optically thick and traces variations of disk temperature instead of gas surface-density variations, while the C18O peaks slightly further away at around 60 au. We compare our observations with hydrodynamical simulations that include gas and dust evolution, and conclude that a 10 MJup mass planet at 60 au and in an eccentric orbit (e = 0.1) can qualitatively explain most of the observed structures. A planet in a circular orbit leads to a much narrower concentration in the millimeter emission, while a planet in a more eccentric orbit leads to a very eccentric cavity as well. In addition, the outer spiral arm launched by the planet changes its pitch angle along the spiral due to the eccentricity and when it interacts with the vortex, potentially appearing in observations as two distinct spirals. Our observations and models show that LkHα 330 is an interesting target to search for (eccentric-) planets while they are still embedded in their parental disk, making it an excellent candidate for studies on planet-disk interaction.