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