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Post Info TOPIC: Fermi Bubble
Blobrana


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Fermi Bubbles
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Title: Supernovae vs. AGN: Clues to the origin of Fermi Bubbles from OVIII/OVII line ratio
Author: Kartick C. Sarkar, Biman B. Nath, Prateek Sharma

We constrain the origin of Fermi Bubbles using 2D hydrodynamical simulations of both star formation driven and black hole accretion driven wind models. We compare our results with recent observations of OVIII to OVII line ratio within and near Fermi Bubbles. Our results suggest that independent of the driving mechanisms, a low luminosity (L ~ 5 - 7 x 10^40 erg s^-1) energy injection best reproduces the observed line ratio for which the shock temperature is \approx 3 x 10^6 K. Assuming the Galactic halo temperature to be 2 x 10^6K, we estimate the shock velocity to be ~300 km s^-1. The corresponding estimated age of the Fermi bubbles is ~15 - 20 Myr. Such an event can be produced either by a star formation rate of ~0.5 solar masses yr^-1 at the Galactic centre or a very low luminosity jet/accretion wind arising from the central black hole.

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Blobrana


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RE: Fermi Bubble
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Title: Search for a neutrino emission from the Fermi Bubbles with the ANTARES telescope
Authors: Simone Biagi

ANTARES is the largest neutrino telescope in the Northern hemisphere. The main scientific goal is the search for cosmic neutrinos coming from galactic and extragalactic sources. Neutrinos are detected through the Cherenkov light emitted along the path of charged particles produced in neutrino interactions inside or in the vicinity of the detector. ANTARES is sensitive to all flavours though it is optimised for muon neutrinos. The detector has been taking data in its complete configuration since May 2008.
Using data collected in the period 2007-2010, the first analysis devoted to the search for neutrinos from the Fermi Bubbles is presented. The Fermi Bubbles are characterised by gamma emission with a E^{-2} spectrum and a relatively constant intensity all over the space. According to a proposed hadronic mechanism for this gamma-ray emission, the Fermi Bubbles can be a source of high-energy neutrinos. No evidence of a neutrino signal is found in the ANTARES data. Therefore upper limits are calculated for neutrino fluxes with different energy cutoffs.

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Blobrana


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Giant Energetic Bubbles Adorn The Milky Way

Two 30,000-light-year long blobs called Fermi bubbles have been discovered on either side of our galactic plane.
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Blobrana


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Title: Origin of the Fermi Bubble
Authors: K.S. Cheng, D. O. Chernyshov, V. A. Dogiel, C.-M. Ko, W.-H. Ip

Fermi has discovered two giant gamma-ray-emitting bubbles that extend nearly 10kpc in diameter north and south of the galactic centre (GC). The existence of the bubbles was first evidenced in X-rays detected by ROSAT and later WMAP detected an excess of radio signals at the location of the gamma-ray bubbles. We propose that periodic star capture processes by the galactic supermassive black hole, Sgr A*, with a capture rate 3 x  10^{-5}yr^{-1} and energy release ~ 3 x  10^{52}erg per capture can produce very hot plasma ~ 10keV with a wind velocity ~ 10^8cm/s injected into the halo and heat up the halo gas to ~ 1keV, which produces thermal X-rays. The periodic injection of hot plasma can produce shocks in the halo and accelerate electrons to ~TeV, which produce radio emission via synchrotron radiation, and gamma-rays via inverse Compton scattering with the relic and the galactic soft photons.

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