The following document lists the file abstract/GBLAKE_DISKS_H2.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
Despite their obvious importance to stellar and planetary formation, our quantitative understanding of circumstellar accretion disks -- in particular their radial and vertical temperature and density structure and gas survival timescales -- remains poor. Here we propose to conduct observations of the pure rotational lines of molecular hydrogen in T Tauri circumstellar disks. These spectral lines, observable only with the SWS aboard ISO, are particularly sensitive to warm, dense gas and thereby provide astronomers with a new probe of the critical 1-30 AU region in potential planet forming disks around young stellar objects (YSOs). Because they arise from the dominant chemical species in the dense interstellar medium and have well characterized oscillator strengths, rotational H2 transitions may also provide a direct and unambigous tracer of the mass in the inner regions of circumstellar disks. Our sample of YSO's has been selected from the Taurus-Auriga and Ophiuchus dark molecular clouds, two of the richest and best-studied nearby clouds of low mass star formation (of which Taurus is only now becoming accessible to ISO), on the basis of their continuum spectral energy distributions (SEDs). Specifically, the suite of solar mass T Tauri stars and related Ae stars chosen are known to have SEDs from infrared to (sub)millimeter wavelengths that are dominated by emission from the circumstellar accretion disk and not surrounding cloud material. The relative H2 line strengths will contain a great deal of information on the vertical and radial temperature profiles, while the overall intensities will accurately constrain the total gas mass in the inner disks for the first time. Combined with stellar evolution models, the ISO data will also bear directly on the gas survival time scales around T Tauri stars.