Quick search Find article
Quick search
Find article

The AGASA and SUGAR Anisotropies and TeV Gamma Rays from the Galactic Center: A Possible Signature of Extremely High Energy Neutrons

FREE

Roland M. Crocker1,2, Marco Fatuzzo3, J. R. Jokipii4, Fulvio Melia5 and Raymond R. Volkas2

Show affiliations


Recent analysis of data sets from two extensive air shower cosmic-ray detectors shows tantalizing evidence of an anisotropic overabundance of cosmic rays toward the Galactic center region that "turns on" around 1018 eV. We demonstrate that the anisotropy could be due to neutrons created in the Galactic center region through charge exchange in proton-proton collisions, where the incident, high-energy protons obey a ~E-2 power law associated with acceleration at a strong shock. We show that the normalization supplied by the gamma-ray signal from EGRET GC source 3EG J1746-2851 (ascribed to p-p-induced neutral pion decay at GeV energies), together with a very reasonable spectral index of 2.2, predicts a neutron flux at ~1018 eV fully consistent with the extremely high energy cosmic-ray data. Likewise, the normalization supplied by the very recent GC data from the HESS air Cerenkov telescope at ~TeV energies is almost equally compatible with the ~1018 eV cosmic-ray data. Interestingly, however, the EGRET and HESS data appear to be themselves incompatible. We find a plausible resolution of this discrepancy in an effective two-source model. Finally, we argue that the shock acceleration is probably occurring in the shell of Sagittarius A East, an unusual supernova remnant located very close to the Galactic center. In support of this contention we note that (1) the extended shell of this object could provide both of the sources suggested by the gamma-ray data and (2) the unusually strong magnetic field at this remnant, together with a perpendicular shock geometry, allow for acceleration of protons up to the extreme energies required to explain the cosmic-ray anisotropy. If the connection between the anisotropy and Sagittarius A East could be firmly established, it would be the first direct evidence for a particular Galactic source of cosmic rays up to energies near 1019 eV.


Subject headings

acceleration of particles; cosmic rays; Galaxy: center; radiation mechanisms: non-thermal; supernova remnants


Dates

Issue 2 (2005 April 1)

Received 2004 August 6, accepted for publication 2004 December 8



  1. The AGASA and SUGAR Anisotropies and TeV Gamma Rays from the Galactic Center: A Possible Signature of Extremely High Energy Neutrons

    Roland M. Crocker et al. 2005 ApJ 622 892

  2. CO Images of the Central Regions of 20 Nearby Spiral Galaxies

    Kazushi Sakamoto et al. 1999 ApJS 124 403

  3. Deuterium thermal desorption from FeAl thin films

    R Checchetto et al 2002 J. Phys.: Condens. Matter 14 6307

  4. Chandra Detection of the First X-Ray Forest along the Line of Sight to Markarian 421

    Fabrizio Nicastro et al. 2005 ApJ 629 700

  5. An XMM-Newton Observation of the High Magnetic Field Radio Pulsar PSR B0154+61

    M. E. Gonzalez et al 2004 ApJ 610 L37

  6. Microscopic structure of the 90° and 30° partial dislocations in gallium arsenide

    João F Justo et al 2002 J. Phys.: Condens. Matter 14 12749

  7. Random tilings: concepts and examples

    C Richard et al 1998 J. Phys. A: Math. Gen. 31 6385

  8. Structure in the parameter dependence of order and chaos for the quadratic map

    Brian R Hunt and Edward Ott 1997 J. Phys. A: Math. Gen. 30 7067

  9. Dynamical percolation through the Voronoïtessellations

    N Pittet 1999 J. Phys. A: Math. Gen. 32 4611

  10. The Star Formation Rate and Dense Molecular Gas in Galaxies

    Yu Gao and Philip M. Solomon 2004 ApJ 606 271

View by subject




Export








Please login to access our web services, or create an account if you don't yet have one.

You must have cookies enabled in your web browser to be able to login.

Username
Password

Forgotten your password? Get a new one here.