Galactic magnetic deflections and Centaurus A as a UHECR source

We evaluate the validity of leading models of the Galactic magnetic field for predicting UHECR deflections from Cen A. The Jansson-Farrar 2012 GMF model (JF12), which includes striated and random components as well as an out-of-plane contribution to the regular field not considered in other models, gives by far the best fit globally to all-sky data including the WMAP7 22 GHz synchrotron emission maps for Q,?U?&?I and ? 40,000 extragalactic Rotation Measures (RMs). Here we test the models specifically in the Cen A region, using 160 well-measured RMs and the Polarized Intensity from WMAP, nearby but outside the Cen A radio lobes. The JF12 model predictions are in excellent agreement with the observations, justifying confidence in its predictions for deflections of UHECRs from Cen A. We find that up to six of the 69 Auger events above 55 EeV are consistent with originating in Cen A and being deflected ? 18?; in this case three are protons and three have Z = 2?4. Others of the 13 events within 18? must have another origin. In order for a random extragalactic magnetic field between Cen A and the Milky Way to appreciably alter these conclusions, its strength would have to be 80 nG ? far larger than normally imagined.

[1]  S. Vorobiov,et al.  Studies of UHECR propagation in the galactic magnetic field , 2009, 0902.3123.

[2]  T. Wibig,et al.  Heavy Cosmic Ray Nuclei from Extragalactic Sources above 'The Ankle' , 2007, 0712.3403.

[3]  N. T. Thao,et al.  The Cosmic Ray Energy Spectrum and Related Measurements with the Pierre Auger Observatory , 2009, 0906.2189.

[4]  On the interpretation of the cosmic-ray anisotropy at ultra-high energies , 2008, 0804.1088.

[5]  K. Greisen.  End to the cosmic ray spectrum , 1966 .

[6]  F. Aharonian,et al.  Centaurus A as TeV gamma-ray and possible UHE cosmic-ray source , 2009, 0910.2327.

[7]  A. M. Taylor,et al.  EGMF Constraints from Simultaneous GeV-TeV Observations of Blazars , 2011, 1101.0932.

[8]  David T. Fraebel,et al.  Upper limit of the spectrum of cosmic rays , 1966 .

[9]  T. Ensslin,et al.  Radio observational constraints on Galactic 3D-emission models , 2007, 0711.1572.

[10]  Charles D. Dermer,et al.  TIME DELAY OF CASCADE RADIATION FOR TeV BLAZARS AND THE MEASUREMENT OF THE INTERGALACTIC MAGNETIC FIELD , 2010, 1011.6660.

[11]  W. Reich,et al.  The Galactic halo magnetic field revisited , 2010, 1010.4394.

[12]  Ievgen Vovk,et al.  Evidence for Strong Extragalactic Magnetic Fields from Fermi Observations of TeV Blazars , 2010, Science.

[13]  J. Brown,et al.  The Outer Scale of Turbulence in the Magnetoionized Galactic Interstellar Medium , 2008, 0802.2740.

[14]  N. T. Thao,et al.  Studies of Cosmic Ray Composition and Air Shower Structure with the Pierre Auger Observatory , 2009, 0906.2319.

[15]  J. Rachen.  Ultra-high energy cosmic rays from radio galaxies revisited , 2008, 0808.0349.

[16]  M. Wolleben,et al.  A New Model for the Loop I (North Polar Spur) Region , 2007, 0704.0276.

[17]  E. Waxman,et al.  Images of Bursting Sources of High-Energy Cosmic Rays: Effects of Magnetic Fields , 1996, astro-ph/9607059.

[18]  M. Halpern,et al.  Five-Year Wilkinson Microwave Anisotropy Probe (WMAP1) Observations: Galactic Foreground Emission , 2008 .

[19]  G. Farrar,et al.  THE GALACTIC MAGNETIC FIELD , 2012, 1210.7820.

[20]  M. C. Maccarone,et al.  Correlation of the highest energy cosmic rays with nearby extragalactic objects , 2007 .

[21]  S. Ostapchenko,et al.  High energy radiation from Centaurus A , 2008, 0805.2608.

[22]  Extragalactic magnetic fields , 1994 .

[23]  L. Anchordoqui,et al.  Centaurus A as a source of extragalactic cosmic rays with arrival energies well beyond the GZK cutoff , 1995, gr-qc/9511031.

[24]  T. Stanev.  Ultra-high-energy Cosmic Rays and the Large-scale Structure of the Galactic Magnetic Field , 1996, astro-ph/9607086.

[25]  F. P. Israel.  Centaurus A – NGC 5128 , 1998 .

[26]  W. Harris,et al.  The Distance to NGC 5128 (Centaurus A) , 2009, Publications of the Astronomical Society of Australia.

[27]  Neil M. Nagar,et al.  Ultra-high energy cosmic rays detected by the Pierre Auger observatory First direct evidence, and its implications, that a subset originate in nearby radiogalaxies , 2008, 0806.3220.

[28]  S. Fliescher,et al.  Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter , 2010, 1009.1855.

[29]  T. Stanev,et al.  THE CENTAURUS A ULTRAHIGH-ENERGY COSMIC-RAY EXCESS AND THE LOCAL EXTRAGALACTIC MAGNETIC FIELD , 2012, 1203.3197.

[30]  G. Farrar,et al.  A NEW MODEL OF THE GALACTIC MAGNETIC FIELD , 2012, 1204.3662.

[31]  S. Johnston,et al.  The pulsar/supernova remnant connection , 1995 .

[32]  T. Piran,et al.  Violation of the Greisen-Zatsepin-Kuzmin cutoff: a tempest in a (magnetic) Teapot? Why cosmic ray energies above 10(20) eV may not require new physics. , 2000, Physical review letters.

[33]  A. Neronov,et al.  Sensitivity of {gamma}-ray telescopes for detection of magnetic fields in the intergalactic medium , 2009, 0910.1920.

[34]  C. G. T. Haslam,et al.  A 408 MHz all-sky continuum survey. II. The atlas of contour maps. , 1982 .

[35]  L. Stawarz,et al.  High-energy Particle Acceleration and Production of Ultra-high-energy Cosmic Rays in the Giant Lobes of Centaurus A , 2008, 0808.1593.

[36]  Michael Prouza,et al.  The Galactic magnetic field and propagation of ultra-high energy cosmic rays , 2003, astro-ph/0307165.

[37]  W C Brown,et al.  Correlation of the highest-energy cosmic rays with nearby extragalactic objects. , 2007, Science.

[38]  L. Stawarz,et al.  ON THE POSSIBLE ASSOCIATION OF ULTRA HIGH ENERGY COSMIC RAYS WITH NEARBY ACTIVE GALAXIES , 2008, 0805.1260.

[39]  K. Newton-McGee,et al.  DERIVING THE GLOBAL STRUCTURE OF THE GALACTIC MAGNETIC FIELD FROM FARADAY ROTATION MEASURES OF EXTRAGALACTIC SOURCES , 2011, 1103.0814.

[40]  N. Nagar,et al.  Ultra-high energy cosmic rays detected by Auger and AGASA - Corrections for galactic magnetic field deflections, source populations, and arguments for multiple components , 2009, 0912.2131.

[41]  D. Fargion.  Coherent and random UHECR spectroscopy of lightest nuclei along Cen A: Shadows on GZK tau neutrinos spread in a near sky and time , 2009, 0908.2650.

[42]  Katsuhiko Sato,et al.  DOES GALACTIC MAGNETIC FIELD DISTURB THE CORRELATION OF THE HIGHEST ENERGY COSMIC RAYS WITH THEIR SOURCES? , 2009, 0909.1532.

[43]  Melanie Johnston-Hollitt,et al.  FARADAY ROTATION STRUCTURE ON KILOPARSEC SCALES IN THE RADIO LOBES OF CENTAURUS A , 2009, 0910.3458.