New Radio and Optical Study of the Supernova Remnant W44
INSTITUTO DE ASTRONOMIA Y FISICA DEL ESPACIO BUENOS AIRES (ARGENTINA)
Pagination or Media Count:
We present new optical images of the supernova remnant SNR W44 in the H-alpha and S II lines covering the entire source for the first time. We also report on improved radio image of W44 at 1442.5 MHz, obtained after the reprocessing of existing VLA data. A spectral index a of -0.4 was derived for the whole source, without indication of significant spectral variations between 0.3 and 1.4 GHz across the remnant. Accurate multiwavelength comparisons were made based on existing observations of W44 in the different spectral regimes. We find excellent correlation between optical and radio emission along the northwest border of the remnant, suggesting that the optical radiation is originating through radiative cooling of the shocked gas immediately behind the shock front. Some diffuse optical emission is also observed towards the interior of W44, with no clear radio counterpart. We confirm that over most of the source, the bright X-ray emission corresponds with regions of low radio brightness. At the northern border of the remnant, diffuse X-ray emission exactly overlaps the radio and optical radiation. From the study of the immediate environs of W44 we conclude that the remnant is interacting with molecular clouds along the eastern border. Such a scenario is compatible with the filamentary structure of W44, the excitation of OH masers and the apparent lack of optical emission along the eastern border. To the north, an extended atomic cloud surrounds the remnant, although the interaction is not evident in this case.
- Radiofrequency Wave Propagation