Abstract
The nature of the bipolar, γ -ray Fermi bubbles (FB) is still unclear, in part because their faint, high-latitude X-ray counterpart has until now eluded a clear detection. We stack ROSAT data at varying distances from the FB edges, thus boosting the signal and identifying an expanding shell behind the south-west, south-east, and north-west edges, albeit not in the dusty northeast sector near Loop I. A Primakoff-like model for the underlying flow is invoked to show that the signals are consistent with halo gas heated by a strong, forward shock to ~ keV temperatures. Assuming ion-electron thermal equilibrium then implies a ~1056 erg event near the Galactic centre ~7Myr ago. However, the reported high absorption-line velocities suggest a preferential shock-heating of ions, and thus more energetic (~1057 erg), younger (≲3 Myr) FBs.
Original language | English |
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Pages (from-to) | 223-235 |
Number of pages | 13 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 480 |
Issue number | 1 |
DOIs | |
State | Published - 11 Oct 2018 |
Keywords
- Cosmic rays
- Galaxy: centre
- Gamma-rays: ISM-X-rays: ISM
- Shock waves
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science