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| Chemical structure of protoplanetary disks with stationary and variable accretion |
| Tamara Molyarova |
| Institute of Astronomy, Russian Academy of Sciences, Moscow |
| Protoplanetary disks around young stars consist of mixed gas and dust, which sustain a variety of chemical reactions. Physical parameters of disks affect chemistry and can be imprinted in their molecular composition. We use a detailed astrochemical model of protoplanetary disk, in order to find species sensitive to particular disk parameters. Specifically, we are interested in disk gas mass and in recently ended luminosity outbursts. We run a number of models with different disk physical structure and stellar parameters to calculate 2D spatial distributions of chemical components. We analyse total disk abundances of major species and their relation to disk parameters. We show that CO is the best tracer of gas mass, although with considerable uncertainties. Volatile molecules, as NH3, C3H4, C2H6, etc., are sensitive to luminosity rise, and H2CO can indicate outburst activity at long timescales. We explore the behavior of the chemistry and probe the applicability of these results to real objects. |
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| Retention of small charged dust in protoplanetary environments |
| Vitaly Akimkin |
| Institute of Astronomy, Russian Academy of Sciences, Moscow | The collisional evolution of solid material in protoplanetary disks (PPD) is a crucial step in the formation of planetesimals, comets and planets. Although dense PPD environments favour fast dust coagulation, there are several factors that limit the straightforward pathway from interstellar-like sub-micron grains to pebble-size agglomerates. This includes dust grain bouncing, fragmentation, fast drift to the central star and electrostatic repulsion of like-charged grains.
We conducted a theoretical modeling of the dust
coagulation coupled with the dust charging and disk
ionization calculations. We show that the electrostatic
barrier is a strong restraining factor to the dust
coagulation in the micrometer size regime. Sustained
turbulence may help to overcome the electrostatic barrier
for compact grains, but not for fluffy grains. Coulomb
repulsion may keep a significant fraction of dust at
1-10 μm size range in vast regions of PPDs. It has
important implications for explanation of high NIR/MIR
fluxes from PPDs and matrix of chondrites.
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