Morphological Evidence for the eROSITA Bubbles Being Giant and Distant Structures
The Astrophysical Journal Letters(2024)
摘要
There are two contradictory views of the eROSITA bubbles: either a 10
kpc-scale pair of giant bubbles blown by the Galactic center (GC), or a 100
pc-scale local structure coincidentally located in the direction of GC. A key
element of this controversy is the distance to the bubbles. Based on the 3D
dust distribution in the Galactic plane, we found three isolated, distant
(500-800 pc) clouds at intermediate Galactic latitudes. Their projected
morphologies perfectly match the X-ray shadows on the defining features of the
north eROSITA bubble, i.e., the North Polar Spur (NPS) and the Lotus Petal
Cloud (LPC), indicating that both the NPS and LPC are distant with a distance
lower limit of nearly 1kpc. In the X-ray dark region between the NPS and LPC,
we found a few polarized radio arcs and attributed them to the bubble's shock
front. These arcs match up perfectly with the outer border of the NPS and LPC
and provide a way to define the bubble's border. The border defined in this way
can be well described by the line-of-sight tangent of a 3D skewed cup model
rooted in the GC. We conclude that, instead of being two independent, distant
features, NPS and LPC compose a single, giant bubble, which, therefore, is most
plausibly a 10-kpc scale bubble rooted at the GC.
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关键词
Milky Way Galaxy,Interstellar clouds,Diffuse interstellar clouds,Shocks,X-ray surveys,Active galactic nuclei
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