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Fermi Bubble

Fermi Bubble. Z.G.,Xiong. Outline. Observations Theories Simulations Discussion. Observations. Finkbeiner,2004. Bland-Hawthorn & Cohen, 2003. Su et al .,2010. Characteristics: size symmetry uniform common origin morphology spectrum. Theories. Bipolar Galactic wind

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Fermi Bubble

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  1. Fermi Bubble Z.G.,Xiong

  2. Outline • Observations • Theories • Simulations • Discussion

  3. Observations • Finkbeiner,2004

  4. Bland-Hawthorn & Cohen, 2003

  5. Su et al.,2010

  6. Characteristics: • size • symmetry • uniform • common origin • morphology • spectrum

  7. Theories • Bipolar Galactic wind • Echoes of the Last Quasar Outburst • AGN Jet • Cosmic Rays Reservoirs • Star Capture

  8. Bipolar Galactic wind • Bland-Hawthorn，2002 • In accord with the stellar record in the Galactic Center, we infer that a powerful nuclear starburst has taken place within the last several million years • We infer that the Galactic Center is driving large-scale winds into the halo every ∼ 10 − 15 Myr or so.

  9. Echoes of the Last Quasar Outburst • Zubovas,2011 • Here we propose an alternative picture where the bubbles are the remnants of a large–scale wide–angle outflow from the SMBH of our Galaxy. • the well known star formation event in the inner 0.5pc of the Milky Way 6 Myr ago.

  10. We estimate that an accreted mass 2 × 10^3M⊙ is needed for the accretion event to power the observed Fermi–LAT lobes. • This estimate suggests that roughly 50% of the gas was turned into stars, while the rest accreted onto Sgr A∗

  11. AGN Jet Guo，2011 • we show that the bubbles can be created with a recent AGN jet activity about 1 - 3 Myr ago, which was active for a duration of ∼ 0.1 - 0.5 Myr • Roles of viscosity and cosmic ray diffusion

  12. Giant, Multi-Billion-Year-Old Reservoirs of Galactic Center Cosmic Rays • Crocker,2011 • Here we show that the bubbles are naturally explained as due to a population of relic cosmic ray protons and heavier ions injected by processes associated with extremely long timescale (> 8 Gyr) and high areal density star-formation in the Galactic center.

  13. Fermi Bubbles as a Result of Star Capture in the Galactic Center • Dogiel,2011; Cheng,2011; Chernyshov,2011.

  14. processes of star capture by the central black hole • Dogiel et al. (2009d).

  15. Star capture by the central black hole • Plasma heating by subrelativistic protons • The hydrodynamic expansion stage • Shock wave acceleration phase and non-thermal emission

  16. Simulation • AGN Jet • Equations

  17. The Galactic Model

  18. Star Capture • Parameters: the tidal disruption rate; power; …

  19. Shock stucture:

  20. Proton spectrum

  21. Electron spectrum

  22. Space distribution

  23. Interactions between shocks:

  24. Discussion • Young or old? • Leptonic or baryonic? • Common? • Impact • Regulation for CRs

  25. Thank you!

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