A standard scenario of evolution of supernova remnants (SNRs) without
pulsar wind nebulae predicts shell-like morphology in non-thermal
radio and thermal X-rays emitted from under-ionized or ionization
equilibrium plasmas. However, radiative recombination X-rays, which
are direct evidence of over-ionized plasmas, have been detected from 7
Galactic SNRs recently. All of these SNRs are categorized into
mixed-morphology SNRs (MM SNRs) that exhibit center-filled thermal
X-ray morphology. In addition, all the SNRs are detected in GeV/TeV
gamma-rays and interact with molecular clouds/H I gas associated with
star forming regions. Such interactions suggest that progenitors of
the SNRs are massive stars.

As a model of MM SNR of the over-ionized states, we carry out
3D-hydrodynamical calculations for the interactions of expanding
supernova ejecta with the dense circumstellar matter and the rarefied
interstellar medium (ISM) outside. The circumstellar matter is assumed
to be composed of the stellar wind matter blown out by the progenitor
with a realistic anisotropy. After the blast wave of the SNR breaks
out of the circumstellar matter into ISM, the shocked ejecta rapidly
cool due to adiabatic expansion and hence become the over-ionized
state. The ejecta are dominated in the X-ray emission measure. On the
other hand, the blast-shocked ISM shell is faint in X-rays due to low
density but is dominated in radio. Thus the SNR of the over-ionized
plasmas exhibits center-filled various morphology depending on the
viewing angle in X-rays within the radio shell. The shell emits
gamma-rays of luminosity of about 1e33 erg/s, which is lower than
typical value of 1e35-1e36 erg/s observed from MM SNRs. However, if
10% of accelerated protons interact with dense external matter of
density of 100/cc, the pion-decay gamma-ray luminosity would be
enhanced to be comparable to observed values.