377 research outputs found
Revealing signatures of planets migrating in protoplanetary discs with ALMA multi-wavelength observations
Recent observations show that rings and gaps are ubiquitous in protoplanetary
discs. These features are often interpreted as being due to the presence of
planets; however, the effect of planetary migration on the observed morphology
has not been investigated hitherto. In this work we investigate whether
multiwavelength mm/submm observations can detect signatures of planet
migration, using 2D dusty hydrodynamic simulations to model the structures
generated by migrating planets and synthesising ALMA continuum observations at
0.85 and 3 mm. We identify three possible morphologies for a migrating planet:
a slowly migrating planet is associated with a single ring outside the planet's
orbit, a rapidly migrating planet is associated with a single ring inside the
planet's orbit while a planet migrating at intermediate speed generates one
ring on each side of the planet's orbit. We argue that multiwavelength data can
distinguish multiple rings produced by a migrating planet from other scenarios
for creating multiple rings, such as multiple planets or discs with low
viscosity. The signature of migration is that the outer ring has a lower
spectral index, due to larger dust grains being trapped there. Of the recent
ALMA observations revealing protoplanetary discs with multiple rings and gaps,
we suggest that Elias 24 is the best candidate for a planet migrating in the
intermediate speed regime.Comment: Accepted for publication in MNRA
An Inner Disk in the Large Gap of the Transition Disk SR 24S
We report new Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 3
observations at 2.75 mm of the TD around SR 24S with an angular resolution of
0.11'' 0.09'' and a peak signal-to-noise ratio of . We
detect an inner disk and a mostly symmetric ring-like structure that peaks at
0.32'', that is 37 au at a distance of 114.4 pc. The full
width at half maximum of this ring is 28 au. We analyze the observed
structures by fitting the dust continuum visibilities using different models
for the intensity profile, and compare with previous ALMA observations of the
same disk at 0.45 mm and 1.30 mm. We qualitatively compare the results of these
fits with theoretical predictions of different scenarios for the formation of a
cavity or large gap. The comparison of the dust continuum structure between
different ALMA bands indicates that photoevaporation and dead zone can be
excluded as leading mechanisms for the cavity formation in SR 24S disk, leaving
the planet scenario (single or multiple planets) as the most plausible
mechanism. We compared the 2.75 mm emission with published (sub-)centimeter
data and find that the inner disk is likely tracing dust thermal emission. This
implies that any companion in the system should allow dust to move inwards
throughout the gap and replenish the inner disk. In the case of one single
planet, this puts strong constraints on the mass of the potential planet inside
the cavity and the disk viscosity of about 5 and
, respectively
Modelowanie Rozkladu Pól Magnetycznych Sluzacych Do Prowadzenia Wiazki Plazmy Powstajacej W Wyladowaniach Lukowych
Revealing signatures of planets migrating in protoplanetary discs with ALMA multiwavelength observations
Recent observations show that rings and gaps are ubiquitous in protoplanetary
discs. These features are often interpreted as being due to the presence of
planets; however, the effect of planetary migration on the observed morphology
has not been investigated hitherto. In this work we investigate whether
multiwavelength mm/submm observations can detect signatures of planet
migration, using 2D dusty hydrodynamic simulations to model the structures
generated by migrating planets and synthesising ALMA continuum observations at
0.85 and 3 mm. We identify three possible morphologies for a migrating planet:
a slowly migrating planet is associated with a single ring outside the planet's
orbit, a rapidly migrating planet is associated with a single ring inside the
planet's orbit while a planet migrating at intermediate speed generates one
ring on each side of the planet's orbit. We argue that multiwavelength data can
distinguish multiple rings produced by a migrating planet from other scenarios
for creating multiple rings, such as multiple planets or discs with low
viscosity. The signature of migration is that the outer ring has a lower
spectral index, due to larger dust grains being trapped there. Of the recent
ALMA observations revealing protoplanetary discs with multiple rings and gaps,
we suggest that Elias 24 is the best candidate for a planet migrating in the
intermediate speed regime.This work has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG. This work was performed using the DiRAC Data Intensive service at Leicester, operated by the University of Leicester IT Services, which forms part of the STFC DiRAC HPC Facility (www.dirac.ac.uk). The equipment was funded by BEIS capital funding via STFC capital grants ST/K000373/1 and ST/R002363/1 and STFC DiRAC Operations grant ST/R001014/1. DiRAC is part of the National e-Infrastructure. G.R. acknowledges support from the Netherlands Organisation for Scientific Research (NWO, program number 016.Veni.192.233). F.M. acknowledges support from the Royal Society Dorothy Hodgkin Fellowship
The Evolution of Dust Disk Sizes from a Homogeneous Analysis of 1-10 Myr old Stars
We utilize ALMA archival data to estimate the dust disk size of 152
protoplanetary disks in Lupus (1-3 Myr), Chamaeleon I (2-3 Myr), and Upper-Sco
(5-11 Myr). We combine our sample with 47 disks from Tau/Aur and Oph whose dust
disk radii were estimated, as here, through fitting radial profile models to
visibility data. We use these 199 homogeneously derived disk sizes to identify
empirical disk-disk and disk-host property relations as well as to search for
evolutionary trends. In agreement with previous studies, we find that dust disk
sizes and millimeter luminosities are correlated, but show for the first time
that the relationship is not universal between regions. We find that disks in
the 2-3 Myr-old Cha I are not smaller than disks in other regions of similar
age, and confirm the Barenfeld et al. (2017) finding that the 5-10 Myr USco
disks are smaller than disks belonging to younger regions. Finally, we find
that the outer edge of the Solar System, as defined by the Kuiper Belt, is
consistent with a population of dust disk sizes which have not experienced
significant truncation
New insights into the nature of transition disks from a complete disk survey of the Lupus star forming region
Transition disks with large dust cavities around young stars are promising
targets for studying planet formation. Previous studies have revealed the
presence of gas cavities inside the dust cavities hinting at recently formed,
giant planets. However, many of these studies are biased towards the brightest
disks in the nearby star forming regions, and it is not possible to derive
reliable statistics that can be compared with exoplanet populations. We present
the analysis of 11 transition disks with large cavities (>20 AU radius) from a
complete disk survey of the Lupus star forming region, using ALMA Band 7
observations at 0.3" (22-30 AU radius) resolution of the 345 GHz continuum,
13CO and C18O 3-2 observations and the Spectral Energy Distribution of each
source. Gas and dust surface density profiles are derived using the
physical-chemical modeling code DALI. This is the first study of transition
disks of large cavities within a complete disk survey within a star forming
region. The dust cavity sizes range from 20-90 AU radius and in three cases, a
gas cavity is resolved as well. The deep drops in gas density and large dust
cavity sizes are consistent with clearing by giant planets. The fraction of
transition disks with large cavities in Lupus is ~11%, which is inconsistent
with exoplanet population studies of giant planets at wide orbits. Furthermore,
we present a hypothesis of an evolutionary path for large massive disks
evolving into transition disks with large cavities.Comment: 29 pages, 15 figures, Accepted by Ap
Are inner disc misalignments common? ALMA reveals an isotropic outer disc inclination distribution for young dipper stars
Dippers are a common class of young variable star exhibiting day-long dimmings with depths of up to several tens of per cent. A standard explanation is that dippers host nearly edge-on (id ≈ 70°) protoplanetary discs that allow close-in (10 au) disc resolved by ALMA and that inner disc misalignments may be common during the protoplanetary phase. More than one mechanism may contribute to the dipper phenomenon, including accretion-driven warps and ‘broken’ discs caused by inclined (sub-)stellar or planetary companions
Evidence for a massive dust-trapping vortex connected to spirals: Multi-wavelength analysis of the HD 135344B protoplanetary disk
Spiral arms, rings and large scale asymmetries are structures observed in
high resolution observations of protoplanetary disks, and it appears that some
of the disks showing spiral arms in scattered light also show asymmetries in
millimeter-sized dust. HD~135344B is one of these disks. Planets are invoked as
the origin of these structures, but no planet has been observed so far. We
investigate the nature of the asymmetric structure in the HD~135344B disk in
order to understand the origin of the spirals and of the asymmetry seen in this
disk. Ultimately, we aim at understanding whether or not one or more planets
are needed to explain such structures. We present new ALMA sub-0.1" resolution
observations in Band 3 and 4. The high spatial resolution allows us to
characterize the mm-dust morphology of the disk. The low optical depth of
continuum emission probes the bulk of the dust in vortex. Moreover, we combine
the new observations with archival data to perform a multi-wavelength analysis
and to obtain information about the dust distribution and properties inside the
asymmetry. We resolve the asymmetric disk into a symmetric ring + asymmetric
crescent, and observe that: (1) the spectral index strongly decreases at the
center of the vortex, consistent with the presence of large grains; (2) for the
first time, an azimuthal shift of the peak of the vortex with wavelength is
observed; (3) the azimuthal width of the vortex decreases at longer
wavelengths, as expected for dust traps. These features allow to confirm the
nature of the asymmetry as a vortex. Finally a lower limit to the total mass of
the vortex is . Considering the uncertainties involved in
this estimate, it is possible that the actual mass of the vortex is higher and
possibly within the required values () to launch
spiral arms similar to those observed in scattered light.P.P. acknowledges support by NASA through Hubble Fellowship grant HST-HF2-51380.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. M.B. acknowledges funding from ANR of France under contract number ANR-16-CE31-0013 (Planet Forming disks). M.T. has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG. Astrochemistry in Leiden is supported by the European Union A-ERC grant 291141 CHEMPLAN, by the Netherlands Research School for Astronomy (NOVA), and by a Royal Netherlands Academy of Arts and Sciences (KNAW) professor prize
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