Origin of diffuse X-ray emission and ionization in the GC

Abstract

Unlike the time variable iron line emission from molecular clouds which is produced by past activity of Sgr A*, the origin of the diffuse line emission in the Galactic center (GC) region is debated. We investigated the origin of this line emission and a source of H2 ionization within 200 pc central radius. We showed that iron atoms and H2 molecules in the diffuse interstellar medium of the GC are not ionized by the same particles. Iron atoms of the diffuse gas are most likely ionized by X-ray photons emitted by Sgr A* while the molecular hydrogen in the GC region is likely ionized by cosmic rays. Production of the line emission from molecular clouds by cosmic rays (CRs) depends strongly on processes of CR penetration into them. We show that turbulent motions of neutral gas may generate strong magnetic fluctuations in the clouds, which prevent free penetration of CRs into the clouds from outside. We provided also analysis of H2 ionization within 1 pc (CND) central region and showed that the ionization there is likely provided by subrelativistic CRs.