Photoevaporation of the Jovian circumplanetary disk I. Explaining the orbit of Callisto and the lack of outer regular satellites. (arXiv:2005.05132v1 [astro-ph.EP])

Photoevaporation of the Jovian circumplanetary disk I. Explaining the orbit of Callisto and the lack of outer regular satellites. (arXiv:2005.05132v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Oberg_N/0/1/0/all/0/1">N. Oberg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kamp_I/0/1/0/all/0/1">I. Kamp</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cazaux_S/0/1/0/all/0/1">S. Cazaux</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rab_C/0/1/0/all/0/1">Ch. Rab</a>

Context: The Galilean satellites are thought to have formed from a
circumplanetary disk (CPD) surrounding Jupiter. When it reached a critical
mass, Jupiter opened an annular gap in the solar protoplanetary disk (PPD) that
might have exposed the CPD to radiation from the young Sun or from the stellar
cluster in which the Solar System formed. Aims: We investigate the radiation
field to which the Jovian CPD was exposed during the process of satellite
formation. The resulting photoevaporation of the CPD is studied in this context
to constrain possible formation scenarios for the Galilean satellites and
explain architectural features of the Galilean system. Methods: We constructed
a model for the stellar birth cluster to determine the intracluster
far-ultraviolet (FUV) radiation field. We employed analytical annular gap
profiles informed by hydrodynamical simulations to investigate a range of
plausible geometries for the Jovian gap. We used the radiation thermochemical
code ProDiMo to evaluate the incident radiation field in the Jovian gap and the
photoevaporation of an embedded 2D axisymmetric CPD. Results: We derive the
time-dependent intracluster FUV radiation field for the solar birth cluster
over 10 Myr. We find that intracluster photoevaporation can cause significant
truncation of the Jovian CPD. We determine steady-state truncation radii for
possible CPDs, finding that the outer radius is proportional to the accretion
rate $dot{M}^{0.4}$. For CPD accretion rates $dot M < 10^{-12} M_{odot}$
yr$^{-1}$, photoevaporative truncation explains the lack of additional
satellites outside the orbit of Callisto. For CPDs of mass $M_{rm CPD} <
10^{-6.2 M_{odot}}$ , photoevaporation can disperse the disk before Callisto
is able to migrate into the Laplace resonance. This explains why Callisto is
the only massive satellite that is excluded from the resonance.

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