1,067 research outputs found
Circumplanetary disks around young giant planets: a comparison between core-accretion and disk instability
Circumplanetary disks can be found around forming giant planets, regardless
of whether core accretion or gravitational instability built the planet. We
carried out state-of-the-art hydrodynamical simulations of the circumplanetary
disks for both formation scenarios, using as similar initial conditions as
possible to unveil possible intrinsic differences in the circumplanetary disk
mass and temperature between the two formation mechanisms. We found that the
circumplanetary disks mass linearly scales with the circumstellar disk mass.
Therefore, in an equally massive protoplanetary disk, the circumplanetary disks
formed in the disk instability model can be only a factor of eight more massive
than their core-accretion counterparts. On the other hand, the bulk
circumplanetary disk temperature differs by more than an order of magnitude
between the two cases. The subdisks around planets formed by gravitational
instability have a characteristic temperature below 100 K, while the core
accretion circumplanetary disks are hot, with temperatures even greater than
1000 K when embedded in massive, optically thick protoplanetary disks. We
explain how this difference can be understood as the natural result of the
different formation mechanisms. We argue that the different temperatures should
persist up to the point when a full-fledged gas giant forms via disk
instability, hence our result provides a convenient criteria for observations
to distinguish between the two main formation scenarios by measuring the bulk
temperature in the planet vicinity.Comment: 12 pages, 9 figures, 1 table, accepted for publication at MNRA
Modeling gravitational instabilities in self-gravitating protoplanetary disks with adaptive mesh refinement techniques
The astonishing diversity in the observed planetary population requires
theoretical efforts and advances in planet formation theories. Numerical
approaches provide a method to tackle the weaknesses of current planet
formation models and are an important tool to close gaps in poorly constrained
areas. We present a global disk setup to model the first stages of giant planet
formation via gravitational instabilities (GI) in 3D with the block-structured
adaptive mesh refinement (AMR) hydrodynamics code ENZO. With this setup, we
explore the impact of AMR techniques on the fragmentation and clumping due to
large-scale instabilities using different AMR configurations. Additionally, we
seek to derive general resolution criteria for global simulations of
self-gravitating disks of variable extent. We run a grid of simulations with
varying AMR settings, including runs with a static grid for comparison, and
study the effects of varying the disk radius. Adopting a marginally stable disk
profile (Q_init=1), we validate the numerical robustness of our model for
different spatial extensions, from compact to larger, extended disks (R_disk =
10, 100 and 300 AU, M_disk ~ 0.05 M_Sun, M_star = 0.646 M_Sun). By combining
our findings from the resolution and parameter studies we find a lower limit of
the resolution to be able to resolve GI induced fragmentation features and
distinct, turbulence inducing clumps. Irrespective of the physical extension of
the disk, topologically disconnected clump features are only resolved if the
fragmentation-active zone of the disk is resolved with at least 100 cells,
which holds as a minimum requirement for all global disk setups. Our
simulations illustrate the capabilities of AMR-based modeling techniques for
planet formation simulations and underline the importance of balanced
refinement settings to reproduce fragmenting structures.Comment: 12 pages, 12 figures; accepted for publication in A&A; for associated
movie files, see http://timlichtenberg.net/publications/gi1
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