Shocked Molecular Gas in the Supernova Remnants W28 and W44: Near‐Infrared and Millimeter‐Wave Observations

High resolution millimeter-wave and near-infrared observations of thesupernova remnants W28 and W44 reveal extensive shocked molecular gas wheresupernova blast waves are propagating into giant molecular clouds. New COobservations were carried out with the IRAM 30-m and ARO 12-m telescopes, andthe near-infrared observations were with Palomar 200-inch telescope. Thenear-infrared observations reveal shocked H2 emission from both supernovaremnants, showing intricate networks of filaments on arcsec scales, followingthe bright ridges of the radio shells. The CO and CS linewidths, indicative ofthe shock speed, are 20-30 km/s. Both the near-infrared and millimeter-waveemission are attributed to shocks into gas with density >1e3 cm-3. Individualshock structures are resolved in the H2 emission, with inferred edge-on shockthickness ~1e17 cm, consistent with non-dissociative shocks into gas densitiesof 1e3-1e4 cm-3. Bright 1720 MHz OH masers are located within the shocked H2gas complexes and highlight only localized areas where the conditions formasing are optimal. The Halpha and X-ray emission, have morphologies verydifferent from the radio. We find a detailed correlation of the radio and H2emission for some long filaments, indicating cosmic ray acceleration orre-acceleration due to the shocks into moderately dense gas. The differentmorphologies of these two remnants at different wavelengths is explained by ahighly nonuniform structure for giant molecular clouds.Comment: ApJ, in press; several figures in jpg for