Multiple Temperature Components of the Hot Circumgalactic Medium of the Milky Way

Abstract

We present a deep XMM-Newton observation of the Galactic halo emission in the direction of the blazar 1ES 1553+113. In order to extract the Galactic halo component from the diffuse soft X-ray emission spectrum, accurately modeling the foreground components is crucial. Here we present complex modeling of the foregrounds with unprecedented details. A careful analysis of the spectrum yields two-temperature components of the halo gas ({T}₁^em} = {10}^6.25-6.42 K, {T}₂^em}={10}^6.68-6.92 K). We find that these temperatures obtained from the emission spectrum are not consistent with those from the absorption spectrum ({T}₁^ab}={10}^6.07-6.13 K, {T}₂^ab}={10}^6.96-7.15 K), unlike the previous studies that found only one-temperature component of the Milky Way circumgalactic medium. This provides us with interesting insights into the nature of emitting and absorbing systems. We discuss several possibilities objectively, and conclude that most likely we are observing multiple (3-4) discrete temperatures between {10}^5.5 {{K}} and ≥slant {10}⁷ K in the Milky Way circumgalactic medium.