Supervirial Temperature or Neon Overabundance? Suzaku Observations of the Milky Way Circumgalactic Medium
Anjali Gupta, Joshua Kingsbury, Smita Mathur, Sanskriti Das, Massimiliano Galeazzi, Yair Krongold, Fabrizio Nicastro
Abstract
Abstract We analyzed Suzaku and Chandra observations of the soft diffuse X-ray background toward four sight lines with the goal of characterizing the X-ray emission from the Milky Way circumgalactic medium (CGM). We identified two thermal components of the CGM, one at a uniform temperature of kT = 0.176 ± 0.008 keV and the other at temperatures in the range kT = 0.65–0.90 keV. The uniform lower-temperature component is consistent with the Galaxy’s virial temperature (∼10 6 K). The temperatures of the hotter components are similar to that recently discovered (∼10 7 K) in the sight line to blazar 1ES 1553+113, passing close to the Fermi bubble. Alternatively, the spectra can be described by just one lower-temperature component with supersolar neon abundance, once again similar to that found in the 1ES 1553+113 sight line. The additional hot component or the overabundance of Ne is required at a significance of >4 σ , but we cannot distinguish between the two possibilities. These results show that the supervirial temperature gas or an enhanced Ne abundance in the warm-hot gas in the CGM is widespread, and these are not necessarily related to the Fermi bubble.