ALMA CO Observations of the Gamma-Ray Supernova Remnant RX J1713.7–3946: Discovery of Shocked Molecular Cloudlets and Filaments at 0.01 pc Scales
H. Sano, T. Inoue, K. Tokuda, T. Tanaka, R. Yamazaki, S. Inutsuka, F. Aharonian, G. Rowell, M. D. Filipović, Y. Yamane, S. Yoshiike, N. Maxted, H. Uchida, T. Hayakawa, K. Tachihara, Y. Uchiyama, Y. Fukui
Abstract
Abstract RX J1713.7−3946 is a unique core-collapse supernova remnant (SNR) that emits bright TeV gamma-rays and synchrotron X-rays caused by cosmic rays, in addition to interactions with interstellar gas clouds. We report here on results of Atacama Large Millimeter/submillimeter Array 12 CO( J = 1–0) observations toward the northwestern shell of the SNR. We newly found three molecular complexes consisting of dozens of shocked molecular cloudlets and filaments with typical radii of ∼0.03–0.05 pc and densities of ∼10 4 cm −3 . These cloudlets and filaments are located not only along synchrotron X-ray filaments, but also in the vicinity of X-ray hotspots with month- or year-scale time variations. We argue that X-ray hotspots and filaments were generated by shock–cloudlet interactions through magnetic-field amplification up to mG. The interstellar medium density contrast of ∼10 5 , coexistence of molecular cloudlets and low-density diffuse medium of ∼0.1 cm −3 , is consistent with such a magnetic field amplification as well as a wind-bubble scenario. The small-scale cloud structures also affect hadronic gamma-ray spectra considering the magnetic field amplification on surface and inside clouds.