Vertical dust settling is thought to be a general mechanism resulting in the concentration of dust in protoplanetary disk midplanes. Because of instabilities and enhanced densities, rapid dust growth, as well as pebble and boulder formation are expected to occur when high enough dust concentrations are reached at the midplane. Yet, the properties of this dust sub-disk remain unconstrained by direct observations. In this I will briefly present recent ALMA observations of HL Tau and HH 30 and will discuss them in the context of dust settling, highlighting the properties of the dust sub-disk at the midplane. In HL Tau we have shown that the size and contrast of the rings as a function of azimuth imply a very thin dust layer in the midplane (h<2au at r=100au). For HH 30, the edge-on geometry allows to directly measure (i.e. without any modelling) the vertical (and radial) extension of the dust disk. Again the data shows an extremely flat dust disk. We will discuss the thickness of the dust layers and estimate the corresponding increase if dust-to-gas ratio. These two examples provide new, and direct, constraints on the midplane of disks that should be useful in the future to improve (M-)HD simulations of dust evolution.
Unless announced otherwise, the lunch talks start at 12:30 sharp. The approximate duration of the lunch talk is given above, and additional time will be given for questions and discussion following the presentation. Please make sure that you take ample time to pick up your lunch beforehand.
Information for Speakers and Hosts: Talks by internal speakers are limited to 20 minutes, with additional time for questions. Visiting speakers can have up to 30 minutes, with additional time for questions. Hosts are responsible for bringing the speaker to the correct room in ample time to set up laptops etc., and for ensuring the speaker also has time for lunch.
For questions and/or suggestions concerning the lunch talks, please contact Themiya Nanayakkara () or Alvaro Hacar ()).