Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...21110901g&link_type=abstract
American Astronomical Society, AAS Meeting #211, #109.01; Bulletin of the American Astronomical Society, Vol. 39, p.937
Astronomy and Astrophysics
Astronomy
Scientific paper
To date, the analysis of the majority of proto-planetary disks has focused on interpretation of their infrared spectral energy distributions, probing thermal emission from small dust grains. These studies suggested that disks could be divided into those with flared, optically thick surfaces, and those where the bulk of the disk, beyond an annulus at the dust sublimation temperature, lies in shadow. Theoretical studies suggested that the shadowed disks were those with larger grains which had settled closer to the disk midplane, and thus might be associated with older, and lower accretion rate systems. In turn, these were the disks where photo-evaporation was expected to excavate central cavities. High contrast imaging studies have suggested that the division of disks into flared structures and geometrically flatter disks is incorrect, with the majority of the coronagraphically-detected proto-planetary disks having radial surface brightness profiles indicating significant dust settling. In several cases, these are systems with very low current accretion rates, no jets, X-ray emission indicative of stellar activity rather than accretion, and in some cases an absence of gas at terrestrial-planet distances from the star. Where these stars can be dated through co-moving lower mass companions, these stars are among the oldest of the protoplanetary disks, and are typically older than the shadowed disk systems. SED modeling suggests that the central cavities in these systems are significantly larger than is expected from photo-evaporation alone, particularly in systems with gas-rich outer disks. Such disks may, in fact, harbor young, gas giant planets.
This study has been supported by NASA NNH06CC28C, HST-GO-10177.02-A, HST-GO-10864.01-A, Chandra G06-7010A.
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