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Article: The Fermi Bubble as a source of cosmic rays in the energy range >10¹⁵ eV

TitleThe Fermi Bubble as a source of cosmic rays in the energy range >10¹⁵ eV
Authors
KeywordsAcceleration of particles
Galaxies: jets
Galaxy: halo
Shock waves
Issue Date2012
PublisherInstitute of Physics Publishing, Inc. The Journal's web site is located at http://iopscience.iop.org/0004-637X/
Citation
The Astrophysical Journal, 2012, v. 746 n. 2, article no. 116 How to Cite?
AbstractThe Fermi Large Area Telescope has recently discovered two giant gamma-ray bubbles that extend north and south of the Galactic center with diameters and heights of the order of H 10kpc. We suggest that the periodic star capture processes by the Galactic supermassive black hole Sgr A*, with a capture rate of τ -1 cap 3 × 10 -5yr -1 and an energy release of W 3 × 10 52erg per capture, can result in hot plasma injecting into the Galactic halo at a wind velocity of u 10 8cms -1. The periodic injection of hot plasma can produce a series of shocks. Energetic protons in the bubble are re-accelerated when they interact with these shocks. We show that for energy larger than E > 10 15eV, the acceleration process can be better described by the stochastic second-order Fermi acceleration. We propose that hadronic cosmic rays (CRs) within the 'knee' of the observed CR spectrum are produced by Galactic supernova remnants distributed in the Galactic disk. Re-acceleration of these particles in the Fermi Bubble produces CRs beyond the knee. With a mean CR diffusion coefficient in this energy range in the bubble D B 3 × 10 30cm 2s -1, we can reproduce the spectral index of the spectrum beyond the knee and within it. The conversion efficiency from shock energy of the bubble into CR energy is about 10%. This model provides a natural explanation of the observed CR flux, spectral indices, and matching of spectra at the knee. © 2012. The American Astronomical Society. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/146408
ISSN
2015 Impact Factor: 5.909
2015 SCImago Journal Rankings: 3.266
ISI Accession Number ID
Funding AgencyGrant Number
NSC-RFBRRP09N04
09-02-92000-HHC-a
GRF of the Government of the Hong Kong SARHKU 7011/10P
Taiwan National Science CouncilNSC 98-2923-M-008-01-MY3
NSC 99-2112-M-008-015-MY3
NSC 97-2112-M-008-011-MY3
Taiwan Ministry of Education under National Central University
Funding Information:

We are very grateful to A. M. Bykov, R. M. Crocker, A. D. Erlykin, Y. Uchiyama, and V. N. Zirakashvili for useful discussions, and to K. F. Sinkov who performed graphic and numerical illustrations of the Kompaneets solution presented in Section 3. D.O.C. and V. A. D. are partly supported by the NSC-RFBR Joint Research Project RP09N04 and 09-02-92000-HHC-a. K. S. C. is supported by the GRF Grants of the Government of the Hong Kong SAR under HKU 7011/10P. C. M. K. is supported by the Taiwan National Science Council Grants NSC 98-2923-M-008-01-MY3 and NSC 99-2112-M-008-015-MY3. W. H. I. is supported by the Taiwan National Science Council Grant NSC 97-2112-M-008-011-MY3 and Taiwan Ministry of Education under the Aim for Top University Program National Central University.

 

DC FieldValueLanguage
dc.contributor.authorCheng, KSen_US
dc.contributor.authorChernyshov, DOen_US
dc.contributor.authorDogel, VAen_US
dc.contributor.authorKo, CMen_US
dc.contributor.authorIp, WHen_US
dc.contributor.authorWang, Yen_US
dc.date.accessioned2012-04-24T07:52:12Z-
dc.date.available2012-04-24T07:52:12Z-
dc.date.issued2012en_US
dc.identifier.citationThe Astrophysical Journal, 2012, v. 746 n. 2, article no. 116en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/10722/146408-
dc.description.abstractThe Fermi Large Area Telescope has recently discovered two giant gamma-ray bubbles that extend north and south of the Galactic center with diameters and heights of the order of H 10kpc. We suggest that the periodic star capture processes by the Galactic supermassive black hole Sgr A*, with a capture rate of τ -1 cap 3 × 10 -5yr -1 and an energy release of W 3 × 10 52erg per capture, can result in hot plasma injecting into the Galactic halo at a wind velocity of u 10 8cms -1. The periodic injection of hot plasma can produce a series of shocks. Energetic protons in the bubble are re-accelerated when they interact with these shocks. We show that for energy larger than E > 10 15eV, the acceleration process can be better described by the stochastic second-order Fermi acceleration. We propose that hadronic cosmic rays (CRs) within the 'knee' of the observed CR spectrum are produced by Galactic supernova remnants distributed in the Galactic disk. Re-acceleration of these particles in the Fermi Bubble produces CRs beyond the knee. With a mean CR diffusion coefficient in this energy range in the bubble D B 3 × 10 30cm 2s -1, we can reproduce the spectral index of the spectrum beyond the knee and within it. The conversion efficiency from shock energy of the bubble into CR energy is about 10%. This model provides a natural explanation of the observed CR flux, spectral indices, and matching of spectra at the knee. © 2012. The American Astronomical Society. All rights reserved.-
dc.languageengen_US
dc.publisherInstitute of Physics Publishing, Inc. The Journal's web site is located at http://iopscience.iop.org/0004-637X/en_US
dc.relation.ispartofThe Astrophysical Journalen_US
dc.rightsThe Astrophysical Journal. Copyright © Institute of Physics Publishing, Inc.en_US
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subjectAcceleration of particles-
dc.subjectGalaxies: jets-
dc.subjectGalaxy: halo-
dc.subjectShock waves-
dc.titleThe Fermi Bubble as a source of cosmic rays in the energy range >10¹⁵ eVen_US
dc.typeArticleen_US
dc.identifier.emailCheng, KS: hrspksc@hkucc.hku.hken_US
dc.identifier.emailChernyshov, DO: chdmit@hku.hken_US
dc.identifier.emailDogel, VA: dogiel@bohr.physics.hku.hken_US
dc.identifier.emailKo, CM: cmko@hku.hk; cmko@astro.ncu.edu.twen_US
dc.identifier.emailWang, Y: yuwang20@hku.hken_US
dc.identifier.authorityCheng, KS=rp00675en_US
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1088/0004-637X/746/2/116-
dc.identifier.scopuseid_2-s2.0-84863176934-
dc.identifier.hkuros199346en_US
dc.identifier.volume746en_US
dc.identifier.issue2, article no. 116en_US
dc.identifier.eissn1538-4357-
dc.identifier.isiWOS:000300406300002-
dc.publisher.placeUnited Statesen_US

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