Akinori Oka, Akio K. Inoue, Taishi Nakamoto, Mitsuhito Honda
We investigate the effect of photodesorption on the snow line position at the
surface of a protoplanetary disk around a Herbig Ae/Be star, motivated by the
detection of water ice particles at the surface of the disk around HD142527 by
Honda et al. For this aim, we obtain the density and temperature structure in
the disk with a 1+1D radiative transfer and determine the distribution of water
ice particles in the disk by the balance between condensation, sublimation, and
photodesorption. We find that photodesorption induced by the far-ultraviolet
radiation from the central star depresses the ice-condensation front toward the
mid-plane and pushes the surface snow line outward significantly when the
stellar effective temperature exceeds a certain critical value. This critical
effective temperature depends on the stellar luminosity and mass, the water
abundance in the disk, and the yield of photodesorption. We present an
approximate analytic formula for the critical temperature. We separate Herbig
Ae/Be stars into two groups on the HR diagram according to the critical
temperature; one is the disks where photodesorption is effective and from which
we may not find ice particles at the surface, and the other is the disks where
photodesorption is not effective. We estimate the snow line position at the
surface of the disk around HD142527 to be 100--300 AU which is consistent with
the water ice detection at >140 AU in the disk. All results depend on the dust
grain size by a complex way and this point requires more work in future.
View original:
http://arxiv.org/abs/1201.1961
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