M. Andersen, J. Rho, W. T. Reach, J. W. Hewitt, J. P. Bernard
We present Spitzer MIPS SED and IRS observations of 14 Galactic Supernova
Remnants previously identified in the GLIMPSE survey. We find evidence for
SNR/molecular cloud interaction through detection of [OI] emission, ionic
lines, and emission from molecular hydrogen. Through black-body fitting of the
MIPS SEDs we find the large grains to be warm, 29-66 K. The dust emission is
modeled using the DUSTEM code and a three component dust model composed of
populations of big grains, very small grains, and polycyclic aromatic
hydrocarbons. We find the dust to be moderately heated, typically by 30-100
times the interstellar radiation field. The source of the radiation is likely
hydrogen recombination, where the excitation of hydrogen occurred in the shock
front. The ratio of very small grains to big grains is found for most of the
molecular interacting SNRs to be higher than that found in the plane of the
Milky Way, typically by a factor of 2--3. We suggest that dust shattering is
responsible for the relative over-abundance of small grains, in agreement with
prediction from dust destruction models. However, two of the SNRs are best fit
with a very low abundance of carbon grains to silicate grains and with a very
high radiation field. A likely reason for the low abundance of small carbon
grains is sputtering. We find evidence for silicate emission at 20 $\mu$m in
their SEDs, indicating that they are young SNRs based on the strong radiation
field necessary to reproduce the observed SEDs.
View original:
http://arxiv.org/abs/1110.4224
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