Fermi Bubble
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Transcript of Fermi Bubble
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Fermi Bubble
Z.G.,Xiong
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Outline
• Observations• Theories• Simulations• Discussion
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Observations
• Finkbeiner,2004
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• Bland-Hawthorn & Cohen, 2003
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• Su et al.,2010
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• Characteristics:• size• symmetry• uniform• common origin• morphology• spectrum
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Theories
• Bipolar Galactic wind• Echoes of the Last Quasar Outburst• AGN Jet• Cosmic Rays Reservoirs• Star Capture
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• 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.∼
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• 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.
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• 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∗
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• 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
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• 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.
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• Fermi Bubbles as a Result of Star Capture in the Galactic Center
• Dogiel,2011; Cheng,2011; Chernyshov,2011.
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• processes of star capture by the central black hole• Dogiel et al. (2009d).
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• Star capture by the central black hole• Plasma heating by subrelativistic protons• The hydrodynamic expansion stage• Shock wave acceleration phase and non-
thermal emission
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Simulation
• AGN Jet• Equations
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• The Galactic Model
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• Star Capture• Parameters: the tidal disruption rate; power; …
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• Shock stucture:
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• Proton spectrum
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• Electron spectrum
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• Space distribution
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• Interactions between shocks:
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Discussion
• Young or old?• Leptonic or baryonic?• Common?• Impact• Regulation for CRs
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Thank you!