EPoS Contribution
EPoS Contribution
Searching for Residual Gas and Dust in Protostellar Disks

Greg Doppmann
WMKO, Kamuela, US
Residual gas in disks around young stars can spin down stars, circularize the orbits of terrestrial planets, and whisk away the dusty debris that is expected to serve as a signpost of terrestrial planet formation. We have carried out a sensitive search for residual gas and dust in the terrestrial planet forming region surrounding protostellar systems across a range in disk evolution. Using high resolution 4.7 micron spectra of classical T Tauri stars, transition objects, and weak T Tauri stars, we searched for weak continuum excess and CO fundamental emission, after making making a careful correction for the stellar contribution to the observed spectrum. We find that the CO emission from transition objects is weaker and located further from the star than CO emission from non-transition T Tauri stars with similar accretion rates. Some weak T Tauri stars have weak M-band veiling, but none show CO emission down to low flux levels (5 x 10-20 to 10-18 W m-2). Does the gaseous component in protostellar disks persist long enough to spin down stars to explain the slow rotation rates observed in older stars? And is the unexpected discrepancy between the high frequency of Earth-mass exoplanets within an AU of mature sun-like stars (~20%) and the low incidence rate (few %) of the warm debris that their formation is expected to produce explained by a long-lived dilute reservoir of residual gas that removes debris through aerodynamic drag and radiation pressure? I will discuss our recent results that probe the extent and lifetime of gas residing in protostellar disks and the important implications for planet formation and stellar rotation.
Caption: CO line profiles obtained by averaging low_J R-branch lines (dotted red lines) and high-J P-branch lines (solid blue lines). The narrow profile observed in transition disk objects (left panels) indicates that the CO emission originates further away from the protostar than the less eveolved classical T Tauri objects that have broadened profiles characteristic of disk rotation (right panels).
Collaborators:
J. Najita, NOAO, US
J. Carr, NRL, US
Key publication

Suggested Session: Protostellar disks