2012ApJ...744..160S

We present an infrared (IR) study of the supernova remnant (SNR) N49 in the Large Magellanic Cloud with the near-IR (NIR; 2.5-5 µm) spectroscopic observations performed by AKARI. The observations were performed as a coarse spectral mapping to cover most of the bright region in the east, which enables us to compare the distribution of various line emissions and to examine their correlation. We detect the 3.3 µm aromatic feature in the remnant, which is the first time the presence of the 3.3 µm aromatic feature related to an SNR has been reported. In the line maps of the H₂1-0 O(3), the 3.3 µm feature, and the Brα, the distribution of the aromatic feature shows overall correlation with those of other emissions together with regional differences that reflect the local physical conditions. By comparing other archival imaging data at different wavelengths, the association of the aromatic emission with other ionic/molecular emissions is clarified. We examine the archival Spitzer Infrared Spectrograph data of N49 and find signatures of other polycyclic aromatic hydrocarbon (PAH) features at 6.2, 7.7, and 11.3 µm corresponding to the 3.3 µm aromatic feature. Based on the band ratios of the PAHs, we find that the PAHs in N49 are not only dominantly neutral, but they are also small in size. We discuss the origin of the PAH emission in N49 and conclude that the emission is either from the PAHs that have survived the shock or from the PAHs in the preshock gas that was heated by the radiative precursor.