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G. Schneider (Steward Obs., U. Az.), HST GO 10177 Team
After decades of concerted effort applied to understanding the formation processes that gave birth to our solar system, the detailed morphology of circumstellar material that must eventually form planets has been virtually impossible to discern until recently. The advent of high contrast coronagraphic imaging, as implemented with the instruments aboard HST, has dramatically enhanced our understanding of natal planetary system formation. Even so, only a handful of evolved disks (appx. 1 Myr and older) have been imaged and spatially resolved in light scattered from their constituent grains. To elucidate the physical processes and properties in potentially planet-forming circumstellar disks, and to understand the nature and evolution of their grains, a larger spatially resolved and photometrically reliable sample of such systems are being observed. We are carrying out a highly sensitive circumstellar disk imaging survey of a well-defined and carefully selected sample of YSOs (1-10 Myr T Tau and HAeBe stars) and (appx. 10 Myr and older) main sequence stars, to probe the posited epoch of planetary system formation, and to provide this critically needed imagery. Our resolved images, which probe to within 0.3 arcseconds of our target stars, are shedding light on the spatial distributions of the dust in disk systems. Combining spatially resolved scattered-light imagery of circumstellar disks with their long wavelength SEDs, the physical properties of the grains may be discerned or constrained by our photometrically accurate surface brightness sensitivity limits for faint disks which elude detection. Our fifty-two target sample builds on the success of the exploratory GTO 7233 program, using two-roll per orbit PSF-subtracted NICMOS coronagraphy, to provide the highest detection sensitivity to the smallest disks around bright stars which can be imaged with HST. We report on the status of this program, and highlight some preliminary results from selected disk systems. Our overall sample will provide critically needed information to help discriminate between proposed evolutionary scenarios in the epochs of planet-building while providing a legacy of cataloged morphologies for interpreting mid- and far-IR SEDs that the Spitzer Space Telescope is now delivering . Support for this work was provided by NASA through grant number GO-10177 from STScI, operated by the Association of Universities for Research in Astronomy Incorporated, under NASA contract NAS5-26555.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.