Searching for SNR/molecular cloud signatures in the low radio frequency spectrum of W44

CASTELLETTI G., DUBNER G., BROGAN G., KASSIM N.E.

Capilla del Monte, Córdoba, Argentina, 18 al 22 de septiembre

Congreso; 49a Reunión Anual de la Asociación Argentina de Astronomía; 2006

Asociación Argentina de Astronomía

We report on the results of long wavelength observations of the Galactic supernova remnant (SNR) W44 (G34.7-0.4) carried out using the Very Large Array (VLA) at 74 MHz (~4m) and 324 MHz (~1m). Several works have proposed that W44 is interacting with neighbouring molecular clouds.  The new images of W44, obtained with unprecedented  sensitivity and resolution at these low radio frequencies, have allowed us to perform a detailed study of the spectrum, identifying for the first time the spectral signatures of the interaction between W44 and the ambient molecular gas. From the comparison of the new observations with archival VLA data at 1442 MHz, we find that the bright filamentary structure in the southeast portion of the remnant, where most of the molecular gas has been observed, has a flatter spectral index as compared to the west hemisphere of the source. In the investigated radio frequencies, no evidence for a spectral connection between  the pulsar wind nebula created by PSR B1853+01 and the surrounding SNR radio shell, is observed.