Associated Molecular and Atomic Clouds with X-Ray Shell of Superbubble 30 Doradus C in the LMC
Filipović, M. D.; Aharonian, F.; Rowell, G.; Fukui, Y.; Onishi, T.; Bamba, A.; Mitsuishi, I.; Maxted, N.; Sano, H.; Fukuda, T.; Yoshiike, S.; Kawamura, A.; Voisin, F.; Mizuno, N.; Tachihara, K.; Yamane, Y.; Inoue, T.; Inutsuka, S.; Tokuda, K.; Fujii, K.; Tsuge, K.; Babazaki, Y.; Inaba, T.
Japan, Australia, Germany, Ireland, Armenia
Abstract
30 Doradus C is a superbubble that emits the brightest non-thermal X- and TeV gamma-rays in the Local Group. To explore the detailed connection between the high-energy radiation and the interstellar medium, we have carried out new CO and HI observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), Atacama Submillimeter Telescope Experiment, and the Australia Telescope Compact Array with resolutions of up to 3 pc. The ALMA data of 12CO(J = 1-0) emission revealed 23 molecular clouds, with typical diameters of ~6-12 pc and masses of ~600-10,000 M⊙. A comparison with the X-rays of XMM-Newton at ~3 pc resolution shows that X-rays are enhanced toward these clouds. The CO data were combined with the HI to estimate the total interstellar protons. A comparison of the interstellar proton column density and the X-rays revealed that the X-rays are enhanced with the total proton column density. These are most likely to be caused by the shock-cloud interaction, which is modeled by magnetohydrodynamical simulations (Inoue et al. 2012). We also note a trend for the X-ray photon index to vary with distance from the center of the high-mass star cluster. This suggests that the cosmic-ray electrons are accelerated by one or multiple supernovae in the cluster. Based on these results, we discuss the role of the interstellar medium in cosmic-ray particle acceleration.