344 research outputs found
Debris Disks in the Scorpius-Centaurus OB Association Resolved by ALMA
We present a CO(2-1) and 1240 um continuum survey of 23 debris disks with
spectral types B9-G1, observed at an angular resolution of 0.5-1 arcsec with
the Atacama Large Millimeter/Submillimeter Array (ALMA). The sample was
selected for large infrared excess and age ~10 Myr, to characterize the
prevalence of molecular gas emission in young debris disks. We identify three
CO-rich debris disks, plus two additional tentative (3-sigma) CO detections.
Twenty disks were detected in the continuum at the >3-sigma level. For the 12
disks in the sample that are spatially resolved by our observations, we perform
an independent analysis of the interferometric continuum visibilities to
constrain the basic dust disk geometry, as well as a simultaneous analysis of
the visibilities and broad-band spectral energy distribution to constrain the
characteristic grain size and disk mass. The gas-rich debris disks exhibit
preferentially larger outer radii in their dust disks, and a higher prevalence
of characteristic grain sizes smaller than the blowout size. The gas-rich disks
do not exhibit preferentially larger dust masses, contrary to expectations for
a scenario in which a higher cometary destruction rate would be expected to
result in a larger mass of both CO and dust. The three debris disks in our
sample with strong CO detections are all around A stars: the conditions in
disks around intermediate-mass stars appear to be the most conducive to the
survival or formation of CO.Comment: 16 pages, 6 figures, accepted for publication in Ap
Resolved Millimeter Observations of the HR 8799 Debris Disk
We present 1.3 millimeter observations of the debris disk surrounding the HR
8799 multi-planet system from the Submillimeter Array to complement archival
ALMA observations that spatially filtered away the bulk of the emission. The
image morphology at arcsecond (150 AU) resolution indicates an optically
thin circumstellar belt, which we associate with a population of dust-producing
planetesimals within the debris disk. The interferometric visibilities are fit
well by an axisymmetric radial power-law model characterized by a broad width,
. The belt inclination and orientation parameters are
consistent with the planet orbital parameters within the mutual uncertainties.
The models constrain the radial location of the inner edge of the belt to
AU. In a simple scenario where the chaotic zone
of the outermost planet b truncates the planetesimal distribution, this inner
edge location translates into a constraint on the planet~b mass of M. This mass estimate is consistent with
infrared observations of the planet luminosity and standard hot-start
evolutionary models, with the uncertainties allowing for a range of initial
conditions. We also present new 9 millimeter observations of the debris disk
from the Very Large Array and determine a millimeter spectral index of
. This value is typical of debris disks and indicates a power-law
index of the grain size distribution , close to predictions for
a classical collisional cascade.Comment: 18 pages, 7 figures, accepted by Ap
Resolving The Moth at Millimeter Wavelengths
HD 61005, also known as "The Moth," is one of only a handful of debris disks
that exhibit swept-back "wings" thought to be caused by interaction with the
ambient interstellar medium (ISM). We present 1.3 mm Submillimeter Array (SMA)
observations of the debris disk around HD 61005 at a spatial resolution of 1.9
arcsec that resolve the emission from large grains for the first time. The disk
exhibits a double-peaked morphology at millimeter wavelengths, consistent with
an optically thin ring viewed close to edge-on. To investigate the disk
structure and the properties of the dust grains we simultaneously model the
spatially resolved 1.3 mm visibilities and the unresolved spectral energy
distribution. The temperatures indicated by the SED are consistent with
expected temperatures for grains close to the blowout size located at radii
commensurate with the millimeter and scattered light data. We also perform a
visibility-domain analysis of the spatial distribution of millimeter-wavelength
flux, incorporating constraints on the disk geometry from scattered light
imaging, and find suggestive evidence of wavelength-dependent structure. The
millimeter-wavelength emission apparently originates predominantly from the
thin ring component rather than tracing the "wings" observed in scattered
light. The implied segregation of large dust grains in the ring is consistent
with an ISM-driven origin for the scattered light wings.Comment: 10 pages, 6 figure
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