High Rydberg state carbon recombination lines toward Cassiopeia A: 332 MHz VLA observations and comparison with H I and molecular lines

Abstract

We present observations of the C270 alpha carbon recombination line, 21 cm neutral hydrogen line and (12)CO (J = 1 right arrow 0) molecular line toward Cas A. A comparison of the distribution of recombination line optical depths over the face of Cas A with that of H I optical depths and molecular line emission favors the association of C270 alpha regions with H I rather than molecular clouds. The association makes it possible to self-consistently determine several physical parameters of the clouds by combining the recombination line and 21 cm H I measurements.