342 research outputs found
Reseña de herramientas de SIG libre
Este artÃculo tiene como objetivo recopilar, en el menor espacio posible, el abanico de opciones de software FOSS4G disponible actualmente. La reseña también se encuentra publicada en wiki.osgeo.org/wiki/Reseñas_FOSS4G.Peer Reviewe
Protoplanetary disks including radiative feedback from accreting planets
While recent observational progress is converging on the detection of compact
regions of thermal emission due to embedded protoplanets, further theoretical
predictions are needed to understand the response of a protoplanetary disk to
the planet formation radiative feedback. This is particularly important to make
predictions for the observability of circumplanetary regions. In this work we
use 2D hydrodynamical simulations to examine the evolution of a viscous
protoplanetary disk in which a luminous Jupiter-mass planet is embedded. We use
an energy equation which includes the radiative heating of the planet as an
additional mechanism for planet formation feedback. Several models are computed
for planet luminosities ranging from to Solar luminosities.
We find that the planet radiative feedback enhances the disk's accretion rate
at the planet's orbital radius, producing a hotter and more luminous
environement around the planet, independently of the prescription used to model
the disk's turbulent viscosity. We also estimate the thermal signature of the
planet feedback for our range of planet luminosities, finding that the emitted
spectrum of a purely active disk, without passive heating, is appreciably
modified in the infrared. We simulate the protoplanetary disk around HD 100546
where a planet companion is located at about 68 au from the star. Assuming the
planet mass is 5 Jupiter masses and its luminosity is , we find that the radiative feedback of the planet increases the
luminosity of its au circumplanetary disk from (without feedback) to , corresponding to an
emission of in band after radiative transfer
calculations, a value that is in good agreement with HD 100546b observations.Comment: 12 pages, 12 figures. Accepted for publication in The Astrophysical
Journa
Dusty spirals triggered by shadows in transition discs
Context. Despite the recent discovery of spiral-shaped features in
protoplanetary discs in the near-infrared and millimetric wavelengths, there is
still an active discussion to understand how they formed. In fact, the spiral
waves observed in discs around young stars can be due to different physical
mechanisms: planet/companion torques, gravitational perturbations or
illumination effects. Aims. We study the spirals formed in the gaseous phase
due to two diametrically opposed shadows cast at fixed disc locations. The
shadows are created by an inclined non-precessing disc inside the cavity, which
is assumed to be optically thick. In particular, we analyse the effect of these
spirals on the dynamics of the dust particles and discuss their detectability
in transition discs. Methods. We perform gaseous hydrodynamical simulations
with shadows, then we compute the dust evolution on top of the gaseous
distribution, and finally we produce synthetic ALMA observations of the dust
emission based on radiative transfer calculations. Results. Our main finding is
that mm- to cm-sized dust particles are efficiently trapped inside the
shadow-triggered spirals. We also observe that particles of various sizes
starting at different stellocentric distances are well mixed inside these
pressure maxima. This dynamical effect would favour grain growth and affect the
resulting composition of planetesimals in the disc. In addition, our radiative
transfer calculations show spiral patterns in the disc at 1.6 {\mu}m and 1.3
mm. Due to their faint thermal emission (compared to the bright inner regions
of the disc) the spirals cannot be detected with ALMA. Our synthetic
observations prove however that shadows are observable as dips in the thermal
emission.Comment: 15 pages, 11 figures, accepted for publication in A&
Spiral waves triggered by shadows in transition disks
Circumstellar asymmetries such as central warps have recently been shown to
cast shadows on outer disks. We investigate the hydrodynamical consequences of
such variable illumination on the outer regions of a transition disk, and the
development of spiral arms. Using 2D simulations, we follow the evolution of a
gaseous disk passively heated by the central star, under the periodic forcing
of shadows with an opening angle of 28. With a lower pressure
under the shadows, each crossing results in a variable azimuthal acceleration,
which in time develops into spiral density waves. Their pitch angles evolve
from at the onset, to 11-14,
over 65~AU to 150~AU. Self-gravity enhances the density contrast of the
spiral waves, as also reported previously for spirals launched by planets. Our
control simulations with unshadowed irradiation do not develop structures,
except for a different form of spiral waves seen at later times only in the
gravitationally unstable control case. Scattered light predictions in the
-band show that such illumination spirals should be observable. We suggest
that spiral arms in the case-study transition disk HD~142527 could be explained
as a result of shadowing from the tilted inner disk.Comment: 6 pages, 4 figures, 1 table. Accepted for publication in ApJ
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