A disk-dominated and clumpy circumgalactic medium of the Milky Way seen in X-ray emission
NATURE ASTRONOMY(2020)
Abstract
The Milky Way galaxy is surrounded by a circumgalactic medium 1 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 activity 2 . The circumgalactic medium may also be a repository for baryons seen in the early universe, but undetected locally 3 . The circumgalactic medium has an ionized component at temperatures near 2 × 10 6 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 emission 6 . 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 – 9 .
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Key words
Astronomy and astrophysics,Astronomy and planetary science,Physics,general,Astronomy,Astrophysics and Cosmology
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