Studying the Galactic Contribution to the Soft X-ray Background
Résumé
We introduce results of the first two years of an ongoing Suzaku Key Project for the study of Solar Wind Charge eXchange (SWCX) and a connected investigation focused on Galactic Halo (GH) and Circum-Galactic Medium (CGM). The main focus of the Key Project is to characterize SWCX emission with a three-year monitoring campaign. We are studying the temporal evolution of the Soft X-ray emission towards four nearby 100 pc) high density clouds that absorb almost all the background photons. Comparing the X-ray emission with the product of the ACE and WIND satellites, we are developing a model of the SWCX X-ray contribution as a function of line of sight, position of the Earth and Sun, and the flux of neutrals in the solar wind. In parallel we are analyzing “empty sky” targets a few degrees away from the high-density clouds. The contrast between on- and off-cloud lines of sight is a unique tool to probe GH and/or CGM by removing the SWCX and Local Bubble foreground. The observation of the region around MBM16, in particular, shows no evidence of any absorbed emission, compared to a significant emission from the not-too-far MBM20 region. This is evidence of a strongly patchy GH+CGM scenario, ruling out uniform models.