Knowledge Bank

Recent studies of the Galactic center using the infrared spectrum of H$\mathrm{3+}$ have revealed a high ionization rate of H$2$ on the order of $\zeta$~$\sim$~3$\times$10$^{-15}$s$^{-1}$ in wide regions of the Central Molecular Zone (CMZ), a region with a radius of $\sim$~150~pc at the Galactic center. 882} L70.} So far we have ascribed this ionization rate, which is an order of magnitude higher than in the Galactic disk, to cosmic rays because of a high density of supernova remnants in the CMZ. In view of the abundant intense X-ray sources from 1 keV to several 10 keV in the region, however, there may be a significant ionization by X-rays also. \vspace{0.1 in} We estimate the ionization rate due to X-rays based on the large scale ART-P X-ray map of the Galactic center region. 116.} The calculations proceed in two steps. First we allow for the attenuation of the observed X-rays by the foreground gas to obtain the original intensities of the X-ray sources. 119.} We then use the corrected X-ray flux to calculate ionization rates of H$2$ in the CMZ. The calculation is also related to the heating of the gas by X-rays. Discussion of the details of calculations and the results will be presented.