Fermi bubbles: High-latitude X-ray supersonic shell

Uri Keshet, Ilya Gurwich

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


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 languageEnglish
Pages (from-to)223-235
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 11 Oct 2018


  • Cosmic rays
  • Galaxy: centre
  • Gamma-rays: ISM-X-rays: ISM
  • Shock waves

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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