Gerrit van der Plas (University of Chile)
Thursday November 17th - 11am
IPAG Seminar Room - IPAG
Disks around young stars are where all the planet-forming action happens. However, the specifics of disk dissipation and planet formation are still a hot topic of debate. Recent observations with the Atacama Large Millimeter/submillimeter Array (ALMA) highlight these issues with exquisite images of a few disks (and counting).
One of the long standing issues, for example, is why disks around the more massive Herbig Ae/Be stars seem to split into two families (group I and group II) when classified by the shape of their spectral energy distributions, and why is it that only group I disks are detected in scattered light except for a few rare exceptions. The current paradigm explains this behaviour through degrees of flaring of the outer disk, but a recently proposed scenario poses that group I disks would have a large inner gap based on the presence (or not) of conspicuous PAH lines. Gaps in disks are important for other reasons as well, as they highlight a critical phase in disk dissipation where planets may be forming.
I will present cycle 2 ALMA observations in which we resolve, for the first time, gaps of several tens of au in the disks around the Herbig Ae/Be stars HD 97048 and HD 34282. Our results strongly suggest that this excess does not arise from a flaring disk surface but from the presence of a disk-gap and the consequently warm, directly irradiated, inner edge of the outer disk. These observations also highlight several disk properties that only now can be well probed by observations, and that will help greatly to advance our understanding of disk dissipation and evolution. These are the near-ubiquity of rich substructure in disks, non-keplerian motion and dust radial migration.
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