Contents of: VI/111/./abstract/EVDISHOE_ZZYSO_H2.abs

The following document lists the file abstract/EVDISHOE_ZZYSO_H2.abs from catalogue VI/111.
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This is a proposal for public data sollicited by OTAC to perform additional
searches for the H2 pure rotational lines in circumstellar disks around YSO's.
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 continue the successful
observations of the pure rotational lines of molecular hydrogen in
circumstellar disks around T Tauri and Herbig Ae stars, started with the open
time program GBLAKE.DISKS_H2. 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 and have well characterized
oscillator strengths, rotational H2 transitions may also provide a direct and
unambiguous tracer of the mass in the inner regions of circumstellar disks.
Initial observations of the Ophiuchus region show H2 detections in 3 out of 5
objects (van Dishoeck et al. 1997). We propose here a sample of YSO's selected
from the Taurus-Auriga, Orion and other regions, coordinated by the PI with
the community. Specifically, the selected objects are known to have SEDs from
infrared to (sub)millimeter wavelengths that are dominated by emission from the
circumstellar accretion disk and not the surrounding cloud material, and
complementary millimeter data are available, showing compact emission. 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. The data will be made
public within 1 month of receipt from ESA.



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