投稿者: y.nagai

Where 3-dimensional analysis matters: dust distribution in protoplanetary disks under planet-disk interactions

 Speaker: Jiaqing Bi (Academia Sinica Institute of Astronomy and Astrophysics (ASIAA)/University of Toronto)

Abstract:

Protoplanetary disks are the birthplaces of planets. However, these disks also embed young planets, making them extremely difficult to detect. Substructures within the disks, especially those observed in millimeter-wavelength dust thermal emissions, such as gaps and rings, have been used to suggest the presence of planets. Nevertheless, planet-disk interactions are not the only mechanisms that can explain these features. Therefore, distinguishing substructures caused by planets from those of other origins is crucial for current planet-hunting efforts and understanding the planet formation process. In this talk, I will summarize our recent studies on dust dynamics under planet-disk interactions, utilizing three-dimensional numerical simulations. Our findings show that incorporating the vertical dimension in planet-disk models reveals a wealth of dynamics, leading to possible characteristic features in observations.

Galaxy evolution with galaxy mergers

Speaker: Takanobu Kirihara (Kitami Institute of Technology)

Abstract:

In the framework of hierarchical structure formation based on cold dark matter, galaxies like the Milky Way grow up through numerous interactions and mergers of many less massive galaxies. These signatures are mainly imprinted in the halo region. In recent years, the Gaia project and the Subaru HSC survey have revealed many tidal remnants in the haloes of the Milky Way and Andromeda galaxy, respectively. In this talk, I will provide an overview of the halo formation process revealed by a combination of observations and numerical simulations, referring to recent observational progress. I also focus on the interaction between massive galaxies. I will introduce the relationship between AGN activity, galaxy density, and interaction of galaxies based on our recent observations and numerical simulations. 

Collisional evolution from dust to planets 

Speaker: Hiroshi Kobayashi (Nagoya University)

Abstract:

Planets were believed to form via the accretion of planetesimals
generated from dust grains in protoplanetary disks. However, the
growth of planets is much slower than their migration due to
disk-planet interaction. Comparably rapid growth via pebble
accretion was then proposed, which requires very massive
protoplanetary disks because most pebbles fall into the central
star.  Although planetesimal formation, planetary migration, and
planetary growth have been studied with much effort, the full
evolution path from dust to planets was uncertain.  We have
investigated full collisional evolution from dust to planets.
For collisional evolution, collisional outcomes are not simply
characterized as fragmentation, bouncing, etc. The impact
simulations for dust aggregates showed the detailed
outcomes. According to the outcome model, the growth of dust
grains are not prevent from collisional fragmentation.  We thus
perform the full simulations (DTPSs) for collisional evolution
from dust to planet in whole protoplanetary disks.  Dust growth
with high porosity allows the formation of icy planetesimals in
the inner disk (< 10 au), while pebbles formed in the outer
disk drift to the inner disk and there grow to planetesimals.
The growth of those pebbles to planetesimals suppresses their
radial drift and supplies small planetesimals sustainably in the
vicinity of cores.  This enables rapid formation of sufficiently
massive planetary cores within 0.2-0.4 million years, prior to
the planetary migration.  However, such porous pebbles are
unlikely to reproduce the polarized millimeter wavelength light
observed from protoplanetary disks. We thus investigate gas-giant
core formation with non-porous pebbles via DTPSs. Even non-porous
bodies can grow into planetesimals and massive cores to be gas
giants are also formed in several 100 thousand years. The rapid core
formation is mainly via the accretion of planetesimals produced
by collisional coagulation of pebbles drifting from the outer
disk. The formation mechanism is similar to the case with porous
pebbles, while core formation occurs in a wider
region (5-10 au) than that with porous pebbles.  Although
pebble growth and core formation depends on the disk temperature,
core formation is likely to occur with disk temperatures in
typical optical thick disks around protostars.