Paper: astro-ph/0507292
Date: Tue, 12 Jul 2005 16:10:05 GMT (76kb)

Title: On the Submillimeter Opacity of Protoplanetary Disks

Authors: B.T. Draine (Princeton University)
Comments: Submitted to ApJ. 17 pages, 6 figures
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Solid particles with the composition of interstellar dust and power-law size
distribution dn/da propto a^{-p} for a < a_max with a_{max} > 3 lambda and 3 <
p < 4 will have submm opacity spectral index beta(lambda) = dln(kappa)/dln(nu)
approx (p-3) beta_{ism}, where beta_{ism} approx 1.7 is the opacity spectral
index of interstellar dust material in the Rayleigh limit. For the power-law
index p approx 3.5 that characterizes interstellar dust, and that appears
likely for particles growing by agglomeration in protoplanetary disks, grain
growth to sizes a > 3 mm will result in beta(1 mm) < ~1. Grain growth can
naturally account for beta approx 1 observed for protoplanetary disks, provided
that a_{max} > ~ 3 lambda.

\\ ( http://arXiv.org/abs/astro-ph/0507292 , 76kb)