Molecular and Atomic Clouds Associated with the Gamma-Ray Supernova Remnant Puppis A

We have carried out a study of the interstellar medium (ISM) toward the shell-like supernova remnant (SNR) Puppis A using NANTEN CO and ATCA H i data. We synthesized a comprehensive picture of the SNR radiation by combining the ISM data with the gamma-ray and X-ray distributions. The ISM, both atomic and molecular gas, is dense and highly clumpy, and is distributed all around the SNR, but mainly in the northeast. The CO distribution revealed an enhanced line intensity ratio of CO(J = 2-1)/(J = 1-0) transitions as well as CO line broadening, which indicate shock heating/acceleration. The results support the assertion that Puppis A is located at 1.4 kpc, in the Local Arm. The ISM interacting with the SNR has a large mass of similar to 10(4) M (circle dot), which is dominated by H i, showing good spatial correspondence with the Fermi-LAT gamma-ray image. This favors a hadronic origin of the gamma-rays, while an additional contribution from a leptonic component is not excluded. The distribution of the X-ray ionization timescales within the shell suggests that the shock front ionized various parts of the ISM at epochs ranging over a few to ten thousand years. We therefore suggest that the age of the SNR is around 10(4) yr as given by the largest ionization timescale. We estimate the total cosmic-ray energy W (p) to be 10(47) erg, which is well placed in the cosmic-ray escaping phase of an age-W (p) plot including more than ten SNRs.

Automated summary

A study of the interstellar medium (ISM) towards the supernova remnant (SNR) Puppis A reveals that the ISM is dense and highly clumpy, and is mainly distributed in the northeast. The CO distribution suggests shock heating/acceleration, supporting the assertion that Puppis A is located in the Local Arm. The interaction between the ISM and the SNR suggests a hadronic origin of the gamma-rays, with a possible contribution from a leptonic component.