Extended Data Fig. 1: Comparison between the X-ray surface brightness of the eROSITA all-sky map (0.6-1.0 keV) and the magnetic ridges.

Panel (a) presents the magnetic ridges from Fig. 1(b), with four constant latitude cuts at the roots of the X-ray outer halos. The comparisons between the polarized intensity WMAP-K Band (ref. ⁶) (PI_syn, red) and the 0.6-1.0 keV eROSITA (ref. ⁵) X-ray emission (green) for the four cuts are presented in panel (b). The detected magnetic ridges are clear peaks of the red curves in (b). At the edges of the X-ray outer halo (highlighted in dotted boxes), the enhancements of the polarized synchrotron intensity (PI_syn,max) are observed with an offset of only a few degrees. While the large-scale magnetic structures surrounding the northern cap of the X-ray outer halo appear to largely enclose the Bubble, the same is not obviously true for the southern halo; there, only the southeastern magnetic ridge approaches the cap of the southern X-ray outer halo.