7 research outputs found
The First Detection of Spatially Resolved Mid-Infrared Scattered Light from a Protoplanetary Disk
We report spatially resolved 11.8 micron images, obtained at the W. M. Keck
10 m telescope, of the protoplanetary disk around the pre--main-sequence star
HK Tau B. The mid-infrared morphology and astrometry of HK Tau B with respect
to HK Tau A indicate that the flux observed in the mid-infrared from HK Tau B
has been scattered off the upper surface of its nearly edge-on disk. This is
the first example of a protoplanetary disk observed in scattered light at
mid-infrared wavelengths. Monte Carlo simulations of this disk show that the
extent (FWHM =0."5, or 70 AU) of the scattered light nebula in the mid-infrared
is very sensitive to the dust size distribution. The 11.8 micron measurement
can be best modelled by a dust grain population that contains grains on the
order of 1.5-3 micron in size; grain populations with exclusively sub-micron
grain sizes or power law size distributions that extend beyond 5 micron cannot
reproduce the observed morphology. These grains are significantly larger than
those expected in the ISM implying that grain growth has occurred; whether this
growth is a result of dust evolution within the disk itself or had originally
occurred within the dark cloud remains an open question.Comment: 11 pages, 1 postscript figure, accepted for publication in ApJ
Herschel -PACS observations of [OI] and H2O in Cha II
Gas plays a major role in the dynamical evolution of protoplanetary discs.
Its coupling with the dust is the key to our understanding planetary formation.
Studying the gas content is therefore a crucial step towards understanding
protoplanetary discs evolution. Such a study can be made through spectroscopic
observations of emission lines in the far-infrared, where some of the most
important gas coolants emit, such as the [OI] 3P1-3 P2 transition at 63.18
microns. We aim at characterising the gas content of protoplanetary discs in
the intermediate-aged Chamaeleon II (Cha II) star forming region. We also aim
at characterising the gaseous detection fractions within this age range, which
is an essential step tracing gas evolution with age in different star forming
regions. We obtained Herschel-PACS line scan spectroscopic observations at 63
microns of 19 Cha II Class I and II stars. The observations were used to trace
[OI] and o-H2O at 63 microns. The analysis of the spatial distribution of [OI],
when extended, can be used to understand the origin of the emission. We have
detected [OI] emission toward seven out of the nineteen systems observed, and
o-H2O emission at 63.32 microns in just one of them, Sz 61. Cha II members show
a correlation between [OI] line fluxes and the continuum at 70 microns, similar
to what is observed in Taurus. We analyse the extended [OI] emission towards
the star DK Cha and study its dynamical footprints in the PACS Integral Field
Unit (IFU). We conclude that there is a high velocity component from a jet
combined with a low velocity component with an origin that may be a combination
of disc, envelope and wind emission. The stacking of spectra of objects not
detected individually in [OI] leads to a marginal 2.6sigma detection that may
indicate the presence of gas just below our detection limits for some, if not
all, of them.Comment: 10 pages, 7 figure
Direct Imaging of the HD 35841 Debris Disk: A Polarized Dust Ring from Gemini Planet Imager and an Outer Halo from HST/STIS
We present new high resolution imaging of a light-scattering dust ring and halo around the young star HD 35841. Using spectroscopic and polarimetric data from the Gemini Planet Imager in H-band (1.6 μm), we detect the highly inclined (i = 85°) ring of debris down to a projected separation of ∼12 au (∼0.″12) for the first time. Optical imaging from HST/STIS shows a smooth dust halo extending outward from the ring to >140 au (>1.″4). We measure the ring's scattering phase function and polarization fraction over scattering angles of 22°-125°, showing a preference for forward scattering and a polarization fraction that peaks at ∼30% near the ansae. Modeling of the scattered-light disk indicates that the ring spans radii of ∼60-220 au, has a vertical thickness similar to that of other resolved dust rings, and contains grains as small as 1.5 μm in diameter. These models also suggest the grains have a low porosity, are more likely to consist of carbon than astrosilicates, and contain significant water ice. The halo has a surface brightness profile consistent with that expected from grains pushed by radiation pressure from the main ring onto highly eccentric but still bound orbits. We also briefly investigate arrangements of a possible inner disk component implied by our spectral energy distribution models, and speculate about the limitations of Mie theory for doing detailed analyses of debris disk dust populations
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Direct Imaging of the HD 35841 Debris Disk: A Polarized Dust Ring from Gemini Planet Imager and an Outer Halo from HST/STIS
We present new high resolution imaging of a light-scattering dust ring and halo around the young star HD 35841. Using spectroscopic and polarimetric data from the Gemini Planet Imager in H-band (1.6 μm), we detect the highly inclined (i = 85°) ring of debris down to a projected separation of ∼12 au (∼0.″12) for the first time. Optical imaging from HST/STIS shows a smooth dust halo extending outward from the ring to >140 au (>1.″4). We measure the ring's scattering phase function and polarization fraction over scattering angles of 22°-125°, showing a preference for forward scattering and a polarization fraction that peaks at ∼30% near the ansae. Modeling of the scattered-light disk indicates that the ring spans radii of ∼60-220 au, has a vertical thickness similar to that of other resolved dust rings, and contains grains as small as 1.5 μm in diameter. These models also suggest the grains have a low porosity, are more likely to consist of carbon than astrosilicates, and contain significant water ice. The halo has a surface brightness profile consistent with that expected from grains pushed by radiation pressure from the main ring onto highly eccentric but still bound orbits. We also briefly investigate arrangements of a possible inner disk component implied by our spectral energy distribution models, and speculate about the limitations of Mie theory for doing detailed analyses of debris disk dust populations