AAS 205th Meeting, 9-13 January 2005
Session 136 Classy I and II Protostars
Poster, Thursday, January 13, 2005, 9:20am-4:00pm, Exhibit Hall

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[136.08] Imaging Polarimetry of Young Stellar Objects with ACS and NICMOS: A Study in Dust Grain Evolution

A. S. Cotera (SETI Institute), G. Schneider (Steward Observatory), D. C. Hines, B. A. Whitney (Space Science Institute), D.L. Padgett (SSC), K. R. Stapelfeldt (JPL), D. Potter (Steward Observatory)

We present the first results from our near-IR and optical polarimetric imaging study utilizing NICMOS and ACS on HST. We have selected five Class I and five Class II YSOs to investigate dust grain evolution and segregation as a function age. Most of our targets also have earlier broad band HST images which allows for an intriguing study of time variability in the scattered light morphology. The YSOs observed to date indicate that the polarized light - scattered from dust grains in the disk - has a strong spatial dependence, with the polarization decreasing dramatically toward the disk midplane for some targets. When combined with radiative transfer models of the circumstellar disks, our observations will enable us to explore the scattering geometry of these systems and place constraints on the grain size distributions. During these early stages of low mass star formation, the circumstellar dust grow from the small grains typical of dust in the interstellar medium (ISM), to planetesimals (and eventually planets); constraining the evolution of the dust grain distribution can provide crucial insight into the formation of Solar type planetary systems.

We will also discuss extending this investigation to Class III and full fledged debris disk systems, where the emergence of the star from the envelope will require use of the newly commissioned coronagraphic polarimetry mode on NICMOS.

Support for this work was provided by NASA through grant number GO-10178 from STScI, operated by the Association of Universities for Research in Astronomy Incorporated, under NASA contract NAS5-26555.

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© 2004. The American Astronomical Society.