Southern Fermi Bubble azimuthal asymmetry

Determine whether the southern Fermi Bubble exhibits azimuthal asymmetries at Galactic latitudes b < -7° analogous to those inferred for the northern Fermi Bubble at b > 7°.

Background

The high-velocity, high-latitude neutral clouds in the northern Fermi Bubble display a longitude–velocity asymmetry that is interpreted as evidence for an azimuthally non-symmetric or elliptical outflow structure. The southern data do not provide sufficient coverage to establish whether a comparable asymmetry exists at negative Galactic latitudes.

References

This analysis raises a number of questions, especially about the southern FB, which is relatively undersampled in our data. In particular, does the southern FB show a cutoff of \ clouds around $ z = -2$ kpc, symmetric to that in the north? Is there evidence of azimuthal asymmetries at $b < -7$ as in the north?

— High Velocity Neutral Gas in the Fermi Bubbles: New Kinematic Limits and Spatial Structure  (2608.16754 - Lockman et al., 17 Aug 2026) in Section 8, “Summary and discussion”