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ACS Multiband Coronagraphic Imaging of the Debris Disk around ß Pictoris. David Golimowski. STScI/NRDD 19 Oct 2005. Collaboration. Observations part of HST/ACS GTO debris disk coronagraphic imaging program - PowerPoint PPT Presentation
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ACS Multiband Coronagraphic Imaging of the Debris Disk around ß Pictoris
David Golimowski
STScI/NRDD 19 Oct 2005
Collaboration
Observations part of HST/ACS GTO debris disk coronagraphic imaging program
PI: H. C. Ford (JHU)
Deputy PI: G. D. Illingworth (UCSC/Lick Obs.)
GTO Debris Disk Team:
Mark Clampin (NASA/GSFC)David Ardila (IPAC/SSC)John Krist (JPL)David Golimowski (JHU)
Motivation Only two multiband scattered-light imaging
studies of ß Pic’s disk have been published: Paresce & Burrows (1987) Lecavelier des Etangs et al. (1993)
Ground-based measurements consistent with neutral colors and amin >> 1 µm, but errors are large (15-30%)
Better colors may better constrain grain properties
HST SM-3B: ACS/HRC equipped with high-contrast Lyot coronagraph with broadband filter set
ACS GTO observations of ß Pic HRC coronagraph
images taken in Cycle 12
0".9 radius occulting spot
Short & long exps. in F435W (B), F606W (Broad V), F814W (Broad I)
1 orbit/filter X two orients
Similar images of Pic (A7 IV) taken for PSF reference
PSF-subtracted images
PSF-deconvolved images
Ratio of images before & after PSF deconvolution
Morphology and Brightness
Inner “warp” is clearly resolved as secondary disk inclined by ~5º to outer disk.
Supports notion that giant planet has perturbed planetesimals from main disk into a coplanar orbit.
The main disk (r < 120 AU) has FWHM ~ 11-13 AU, i.e., ~50% narrower than previously measured.
PSF deconvolution is crucial for accurate modeling of the disk.
The radial surface-brightness profiles of the main and secondary disks are not alike.
Single power-law fit of secondary disk suggests:• No depletion of dust down to 80 AU• Smaller/larger ice-sublimation zone than main disk
Uncertainties are 5-10 times smaller than those of previous studies.
Midplane Colors
Grain characteristics
We compared the midplane colors to simulated colors of grain distributions with various compositions, porosities, and minimum grain sizes.
r < 120 AU: Colors matched by compact or moderately porous (P < 75%), non-icy grains of astrosil/graphite with amin ~ 0.15-0.2 µm
10X smaller than ground-based estimates Consistent with cometary activity within 120 AU
r > 120 AU: Icy grains with amin increasing from 0.15 µm at 120 AU to perhaps ~2 µm at 250 AU.
Legacy of ACS ß Pic Study
Our multiband ACS images are the finest optical images of the inner (30-250 AU) region of ß Pic’s disk obtained to date.
These images will not be superseded by TPF and other proposed exoplanet-imaging missions due to tiny FOV. Comparable IR images are expected from JWST if current imaging specs are maintained.
Thus, our results will be a standard reference for comparative and theoretical studies of debris disks for at least a decade.