Abstract
We present HST NICMOS Paschen α (Paα) images and low- and high-resolution IRS spectra of photoevaporating disk-tail systems originally detected at 24 μm near O stars. We find no Paα emission in any of the systems. The resulting upper limits correspond to about (2-3) × 10 -6 M⊙ of mass in hydrogen in the tails, suggesting that the gas is severely depleted. The IRAC data and the low-resolution 5-12 μm IRS spectra provide evidence for an inner disk, while high-resolution long-wavelength (14-30 μm) IRS spectra confirm the presence of a gas-free tail that consists of ∼0.01 to ∼ 1 μm dust grains originating in the outer parts of the circumstellar disks. Overall, our observations support theoretical predictions in which photoevaporation removes the gas relatively quickly (≤ 105 yr) from the outer region of a protoplanetary disk, but leaves an inner, more robust, and possibly gas-rich disk component of radius 5-10 AU. With the gas gone, larger solid bodies in the outer disk can experience a high rate of collisions and produce elevated amounts of dust. This dust is being stripped from the system by the photon pressure of the O star to form a gas-free dusty tail.
Original language | English (US) |
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Pages (from-to) | 408-417 |
Number of pages | 10 |
Journal | Astrophysical Journal |
Volume | 688 |
Issue number | 1 |
DOIs | |
State | Published - Nov 20 2008 |
Keywords
- Circumstellar matter
- Planetary systems: protoplanetary disks
- Stars: formation
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science