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J.E. Bjorkman (University of Toledo), B.A. Whitney (Space Science Institute), K. Wood (University of St Andrews)
We study the effects of a planetary gap on the hydrostatic structure of a proto-planetary disk. Such a gap produces a bright ring surrounding the dark gap in scattered light images because stellar radiation that would have been scattered (and absorbed) by material within in the gap is instead reprocessed by the disk wall at the outer edge of the gap (Varnière et al. 2005). The light absorbed by the outer wall raises its temperature, which increases the disk scale height at that location. As a result, the outer wall of the gap will shadow the outer region of the disk. Here we investigate whether or not this self-shadowing will lead to a collapse of the outer disk as suggested by Dullemond & Dominik (2004).
Using a 3-D Monte Carlo radiation transfer code to determine the disk temperature and hydrostatic structure, we find that the disk scale height at the outer wall is indeed larger, but only over a rather small distance. In particular, we observe that the outer disk does not ``collapse''. This behavior is exactly analogous to that of the inner wall of the disk (at the dust destruction radius). As discussed by Walker et al. (2005), all disks are self-shadowed; collapse only occurs for steep power laws of the surface density (and not for steady-state accretion models). We conclude that the presence of the gap does not significantly alter the overall structure of the disk; it only affects the disk locally in the vicinity of the gap.
This work was supported by NSF grants AST-0307686.
Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.