# Faint X-ray sources resolved in the ASCA Galactic plane survey and their contribution to the Galactic ridge X-ray emission Source: [Faint X-ray sources resolved in the ASCA Galactic plane survey and their contribution to the Galactic ridge X-ray emission]() Collection index: [llms.txt]() Data updated: 2025-10-24T13:32:37.304Z Authors: M. Sugizaki, K. Mitsuda, H. Kaneda, K. Matsuzaki, S. Yamauchi, K. Koyama Published: 2001-01-07T08:05:30.000Z ## Abstract The X-ray emission from the central region of the Galactic plane, \|l\|\<45 deg and \|b\|\<0.4 deg, was studied in the 0.7-10 keV energy band with a spatial resolution of ~3' with the ASCA observatory. We developed a new analysis method for the ASCA data to resolve discrete sources from the extended Galactic ridge X-ray emission (GRXE). We resolved 163 discrete sources with a flux down to 10^-12.5 ergs cm^-2 s^-1 and determined the intensity variations of the GRXE as a function of the Galactic longitude with a spatial resolution of ~1 deg. The longitudinal variation of the GRXE in the energy band above 4 keV shows a large enhancement within \|l\|\<30 deg. This suggests a strong enhancement of X-ray emissivity inside the 4-kpc arms. Searches for identifications of the resolved sources with cataloged X-ray sources and optical stars show that the 66% are unidentified. Spectral analysis of each source shows that a large number of the unidentified sources have hard X-ray spectra. We classified the sources into several groups according to the spectra and analyzed the spectra summed within each group. Possible X-ray origins of these sources are discussed based on the grouping analysis. Also, we derived the LogN-LogS relations of the resolved sources in the energy bands below and above 2 keV. The obtained LogN-LogS relation of the Galactic X-ray sources above 2 keV is represented by a power-law with an index of -0.79+/-0.07. This flat LogN-LogS relation suggests that the spatial distribution of the sources should have an arm-like structure in which the Solar system is included. The integrated surface brightness of the resolved sources is about 10% of the total GRXE in both energy bands. The approximately 90% of the emission remaining is still unresolved. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. ## Original sources and implementation [Original paper]() [PDF]()