Asymmetric eROSITA bubbles as the evidence of a circumgalactic medium wind

Abstract

The eROSITA bubbles are detected via the instrument with the same name. The northern bubble shows noticeable asymmetric features, including distortion to the west and enhancement in the eastern edge, while the southern counterpart is significantly dimmer. Their origins are debated. Here, we performed hydrodynamic simulations showing that asymmetric eROSITA bubbles favor a dynamic, circumgalactic medium wind model, but disfavor other mechanisms such as a non-axisymmetric halo gas or a tilted nuclear outflow. The wind from the east by north direction in Galactic coordinates blows across the northern halo with a velocity of about 200 km s${}^{-1}$, and part of it enters the southern halo. This creates a dynamic halo medium and redistributes both density and metallicity within. This naturally explains the asymmetric bubbles in both the morphology and surface brightness. Our results suggest that our Galaxy is accreting low-abundance circumgalactic medium from one side while providing outflow feedback.

Published in Nature Communications, file size 10MB

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Cited by in corpus (5)

• The SRG/eROSITA diffuse soft X-ray background. I. The local hot bubble in the western Galactic hemisphere
• A magnetised Galactic halo from inner Galaxy outflows
• North Polar Spur: gaseous plume(s) from star-forming regions at $\sim$3-5 kpc from Galactic Center?
• Cosmic-ray electrons and the magnetic field of the North Polar Spur
• Tidal disruption events as the origin of the eROSITA and Fermi bubbles