A Spitzer Space Telescope Infrared Survey of Supernova Remnants in the Inner Galaxy
Using Infrared Array Camera ( IRAC) images at 3.6, 4.5, 5.8, and 8 m from the GLIMPSE Legacy science program on the Spitzer Space Telescope, we searched for infrared counterparts to the 95 known supernova remnants that are located within Galactic longitudes 65 > jlj > 10 and latitudes jbj < 1 . Eighteen infrared counterparts were detected. Many other supernova remnants could have significant infrared emission but are in portions of the Milky Way too confused to allow the separation of bright H ii regions and pervasive mid-infrared emission from atomic and molecular clouds along the line of sight. Infrared emission from supernova remnants originates from synchrotron emission, shock-heated dust, atomic fine-structure lines, and molecular lines. The detected remnants are G11.20.3, Kes 69, G22.70.2, 3C 391, W44, 3C 396, 3C 397, W49B, G54.40.3, Kes 17, Kes 20A, RCW 103, G344.70.1, G346.60.2, CTB 37A, G348.50.0, and G349.7+0.2. The infrared colors suggest emission from molecular lines (nine remnants), fine-structure lines (three remnants), polycyclic aromatic hydrocarbons (four remnants), or a combination; some remnants feature multiple colors in different regions. None of the remnants are dominated by synchrotron radiation at mid-infrared wavelengths. The IRAC-detected sample emphasizes remnants interacting with relatively dense gas, for which most of the shock cooling occurs through molecular or ionic lines in the mid-infrared.
The Astronomical Journal, Vol. 131, 1479–1500, 2006 March.