J/A+A/560/A105 SAO 206462 polarised Ks image (Garufi+, 2013)
Small vs. large dust grains in transitional disks: do different cavity sizes
indicate a planet? SAO 206462 (HD 135344B) in polarized light with VLT/NACO.
Garufi A., Quanz S.P., Avenhaus H., Buenzli E., Dominik C., Meru F.,
Meyer M.R., Pinilla P., Schmid H.M., Wolf S.
<Astron. Astrophys., 560, A105-105 (2013)>
=2013A&A...560A.105G 2013A&A...560A.105G
ADC_Keywords: Stars, pre-main sequence ; Polarization
Keywords: stars: pre-main sequence - protoplanetary disks -
ISM: individual: SAO 206462 - techniques: polarimetric
Abstract:
Transitional disks represent a short stage of the evolution of
circumstellar material. Studies of dust grains in these objects can
provide pivotal information on the mechanisms of planet formation.
Dissimilarities in the spatial distribution of small (µm-size) and
large (mm-size) dust grains have recently been pointed out.
Constraints on the small dust grains can be obtained by imaging the
distribution of scattered light at near-infrared wavelengths. We aim
at resolving structures in the surface layer of transitional disks
(with particular emphasis on the inner 10-50AU), thus increasing the
scarce sample of high-resolution images of these objects. We obtained
VLT/NACO near-IR high-resolution polarimetric differential imaging
observations of SAO 206462 (HD135344B). This technique allows one to
image the polarized scattered light from the disk without any
occulting mask and to reach an inner working angle of ∼0.1". A face-on
disk is detected in H and Ks bands between 0.1" and 0.9". No
significant differences are seen between the H and Ks images. In
addition to the spiral arms, these new data allow us to resolve for
the first time an inner disk cavity for small dust grains. The cavity
size (≃28AU) is much smaller than what is inferred for large dust
grains from (sub-)mm observations (39 to 50AU). This discrepancy
cannot be ascribed to any resolution effect. The interaction between
the disk and potential orbiting companion(s) can explain both the
spiral arm structure and the discrepant cavity sizes for small and
large dust grains. One planet may be carving out the gas (and, thus,
the small grains) at 28AU, and generating a pressure bump at larger
radii (39AU), which holds back the large grains. We analytically
estimate that, in this scenario, a single giant planet (with a mass
between 5 and 15MJ) at 17 to 20AU from the star is consistent with
the observed cavity sizes.
Description:
Fits file containing the non-photometrically calibrated, polarized
emission from the disk around SAO 206462, obtained in Ks band with
VLT/NACO.
Objects:
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RA (2000) DE Designation(s)
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15 15 48.44 -37 09 16.0 SAO 206462 = HD 135344B
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 45 1 List of fits file
fits/* . 1 Fits file
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 24 F5.3 arcsec/pix Scale Scale of the image
26- 28 I3 pix Nx Number of pixels along X-axis
29 A1 --- --- [x]
30- 32 I3 pix Ny Number of pixels along Y-axis
34- 37 I4 Kibyte size Size of FITS file
39- 45 A7 --- FileName Name of FITS file in subdirectory fits
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Acknowledgements:
Antonio Garufi, antonio.garufi(at)phys.ethz.ch
(End) Patricia Vannier [CDS] 28-May-2014