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Session 41 - T Tauri Stars & Protostellar Regions.
Display session, Wednesday, June 11
South Main Hall,
We present model calculations of optical and near IR scattered light images expected from Class II T Tauri stars --- the star plus disk systems. The parameters controlling the disk shape, size, and mass are chosen to be within theoretically and observationally derived limits. We further restrict our models to nearly edge-on disks, since for lower inclinations the central starlight is many orders of magnitude greater than the radiation scattered in the disk. In addition to model flux images, we also calculate spectral energy distributions for pole-on viewing using approximations for flat and flared disks. We find that direct imaging of edge-on disks can only provide estimates of the scale height at large distances from the central star and an estimate of the disk mass. The images are rather insensitive to the degree of flaring, provided the scale height is fixed at large radii.
We apply our modeling techniques to the recent Hubble Space Telescope images of HH30 IRS which appears to show the scattered light for an almost edge-on disk. We have re-investigated these scattered light images and attempted to model them with parameters that are more typical of classical T Tauri stars. We also investigated whether the scattered light images could have been produced by starlight scattering off the walls of jet-carved cavities in infalling envelopes surrounding the more embedded Class I sources. We find that while the Class I infalling envelope plus cavity model qualitatively resembles the HST images, the spatial extent of the model images are too large. Edge-on disk models appear to provide better fits to the data and enable us to determine the disk scale height at large distances from the central star. However, the assumption of axisymmetry and uniform illumination is clearly inadequate for this variable source. In addition to producing flux images, our radiation transfer simulations predict the spatially resolved polarization structure of HH30. We have also performed K band simulations for HH30 in anticipation of high resolution IR imaging polarimetry.
Program listing for Wednesday