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Explaining millimeter-sized particles in brown dwarf disks | P. Pinilla
; T. Birnstiel
; M. Benisty
; L. Ricci
; A. Natta
; C. P. Dullemond
; C. Dominik
; L. Testi
; | Date: |
24 Apr 2013 | Abstract: | Planets have been detected around a variety of stars, including low-mass
objects, such as brown dwarfs. However, such extreme cases are challenging for
planet formation models. Recent sub-millimeter observations of disks around
brown dwarf measured low spectral indices of the continuum emission that
suggest that dust grains grow to mm-sizes even in these very low mass
environments. To understand the first steps of planet formation in scaled-down
versions of T-Tauri disks, we investigate the physical conditions that can
theoretically explain the growth from interstellar dust to millimeter-sized
grains in disks around brown dwarf. We modeled the evolution of dust particles
under conditions of low-mass disks around brown dwarfs. We used coagulation,
fragmentation and disk-structure models to simulate the evolution of dust, with
zero and non-zero radial drift. For the non-zero radial drift, we considered
strong inhomogeneities in the gas surface density profile that mimic long-lived
pressure bumps in the disk. We studied different scenarios that could lead to
an agreement between theoretical models and the spectral slope found by
millimeter observations. We find that fragmentation is less likely and rapid
inward drift is more significant for particles in brown dwarf disks than in
T-Tauri disks. We present different scenarios that can nevertheless explain
millimeter-sized grains. As an example, a model that combines the following
parameters can fit the millimeter fluxes measured for brown dwarf disks: strong
pressure inhomogeneities of $sim$ 40% of amplitude, a small radial extent
$sim$ 15 AU, a moderate turbulence strength $alpha_{mathrm{turb}}= 10^{-3}$,
and average fragmentation velocities for ices $v_f = 10 m s^{-1}$. | Source: | arXiv, 1304.6638 | Services: | Forum | Review | PDF | Favorites |
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