Imaging of Four Galactic Supernovae Remnants in the Mid-Infrared, and
  their Interaction with the Interstellar Medium
  We provide mid-infrared (MIR) imaging, photometry and profiles for the
Galactic supernova remnants (SNRs) G001.0-00.1, G355.9-02.5, G355.6-00.0, and
W28 based upon data deriving for the Galactic Legacy Infrared Midplane Survey
Extraordinaire (GLIMPSE). All of the sources show evidence for interaction with
the interstellar medium (ISM), leading to curved frontal structures and
apparent voids in the ISM. An analysis of the spectral energy distributions
(SEDs) of Class I young stellar objects (YSOs) within the north-westerly
interaction region of W28, and of the density of stars within the borders of
the SNR, suggests that many of them may have been triggered by the SN event.
2-D radiative transfer modelling permits us to constrain the physical
parameters of the sources. It is also noted that the location of Class I YSOs
about the perimeter of G001.0-00.1, and close to frontal arcs associated with
SNR G355.9-02.5, suggests that star formation may have been triggered by these
SNRs as well. Finally, it is found that the MIR colours of the frontal
structures appear consistent with shock excitation of the v = 0->0 transitions
of H2, although it is conceivable that emission by polycyclic aromatic
hydrocarbons (PAHs) may also play a role. Where the latter mechanism is
relevant, then it is possible that emission derives from the shattering of
larger grains in frontal regions, leading to increased volume densities of PAH
carrying grains.
