Search for Charge eXchange emission in the starburst galaxy M82 with the combination of a novel technique of image analysis and high resolution spectroscopy

Recent X-ray studies of starburst galaxies have found that the Charge eXchange (CX) process commonly occurs between the outflowing hot plasma and cold gas, possibly from swept-up clouds. The flux and spatial distribution of the CX emission provide unique clues to directly investigate the interplay between these components. We present an analysis of M82, a prototype starburst galaxy, combining the application of a blind source separation method to CCD data together with RGS high resolution spectroscopy. Applying the technique to CCD data from an XMM observation, we successfully identified a component characterized by the enhanced O-K lines expected from the CX process. We also find that this component shows a compact peak (~2′) in the southern outflow. Analyzing the RGS spectra extracted from the peak, we detect a high forbidden-to-resonance ratio in the O Hea triplet as well as C, N, and O Lya enhanced in the CX process. From an estimation of the CX emitting volume and the presence of complex Ha filaments, our result suggests that CX primarily occurs in a limited region where Ha clumps are disturbed by plasma outflows.