The Milky Way galaxy is surrounded by a circumgalactic medium¹ that may play a key role in galaxy evolution as the source of gas for star formation and a repository of metals and energy produced by star formation and nuclear activity². The circumgalactic medium may also be a repository for baryons seen in the early universe, but undetected locally³. The circumgalactic medium has an ionized component at temperatures near 2 × 10⁶ K studied primarily in the soft-X-ray band^4,5. Here we report a survey of the southern Galactic sky with a soft-X-ray spectrometer optimized to study diffuse soft-X-ray emission⁶. The X-ray emission is best fitted with a disk-like model based on the radial profile of the surface density of molecular hydrogen, a tracer of star formation, suggesting that the X-ray emission is predominantly from hot plasma produced via stellar feedback. Strong variations in the X-ray emission on angular scales of ~10° indicate that the circumgalactic medium is clumpy. Addition of an extended, and possibly massive, halo component is needed to match the halo density inferred from other observations^7,8,9.

银河系被环绕的银河系介质¹包围，该介质在银河系的发展中起着关键作用，它是恒星形成的气体源以及恒星形成和核活动产生的金属和能量的储存库²。绕银河系的媒介也可能是早期宇宙中见到的重子的储存库，但在当地未被发现³。绕银河系介质在2×10 ⁶  K附近的温度下具有电离成分，主要在软X射线谱带^4,5中研究。在这里，我们报告了使用软X射线光谱仪对银河系南部的天空进行的调查，该软X光谱仪经过优化，可用于研究软X射线的扩散⁶。X射线发射最适合基于分子氢的表面密度的径向分布（星状形成的示踪剂）的圆盘状模型，这表明X射线发射主要来自通过恒星反馈产生的热等离子体。X射线发射在〜10°的角度范围内发生强烈变化，表明绕银河系介质很结块。需要增加一个扩展的，可能是大量的光环分量，以匹配从其他观测值^7,8,9推断出的光环密度。