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Hydroxyl lines towards Puppis A


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The 1667-MHz ground-state hydroxyl (OH) line has been observed towards positions on Puppis A as well as in the immediate vicinity of this supernova remnant (SNR). The spectra at two positions on Puppis A show absorption lines at velocities less than +7.6 km s−1, and emission lines above this velocity. Analysis of all four 18 cm OH lines indicates that Puppis A must lie between the OH clouds seen in absorption and emission, giving it a vlsr of +7.6 km s−1. This implies that the kinematic distance to Puppis A is inline image The OH clouds in front of Puppis A are slightly anomalously excited, as shown by analysis of the four 18 cm OH lines at the two observed positions on Puppis A. There is no evidence of any interaction of the SNR with the clouds in front of and behind it.