Paper: astro-ph/0509508
Date: Fri, 16 Sep 2005 18:07:44 GMT (396kb)

Title: Dead Zones and Extrasolar Planetary Properties

Authors: Soko Matsumura, Ralph E. Pudritz

Comments: 18 pages, 11 figures, submitted to MNRAS
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Most low-mass protostellar disks evolve in clustered environments where they
are affected by external radiation fields, while others evolve in more isolated
star-forming regions. Assuming that the magneto-rotational instability (MRI) is
the main source of viscosity, we calculate the size of a poorly ionized, MRI
inactive, and hence low viscosity region - the "dead zone" - in these
protostellar disks. We include disk ionization by X-rays, cosmic rays,
radioactive elements and thermal collisions, recombination by molecules,
metals, and grains, as well as the effect of turbulence stimulation in the dead
zone by the active layers lying above it. We also calculate the gap-opening
masses of planets, which are determined by a disk's viscosity and a disk aspect
ratio, for disks in these environments and compare them with each other.
We show that the dead zone is a robust feature of the protostellar disks that
is largely independent of their environment, typically stretching out to ~ 15
AU. We analyze the possible effects of dead zones on planet formation,
migration, and eccentricity evolution. We show that the gap-opening mass inside
the dead zone is expected to be of the order of terrestrial and ice giant mass
planets while that outside the dead zone is Jovian or super Jovian mass
planets, largely independent of the star-forming environment. We also find that
the growth of eccentricity of massive extrasolar planets is particularly
favorable through the planet-disk interaction that occurs inside the large gaps
that planets can open as they migrate into dead zones.

\\ ( http://arXiv.org/abs/astro-ph/0509508 , 396kb)