1. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 2008 1 Towards unravelling the structural distribution of ultra-high-energy cosmic ray sources Hajime Takami The University of Tokyo JSPS Fellow Ref. HT and K. Sato, arXiv:0710.0767 HT and K. Sato, arXiv:0711.2386 K. Sato (Univ. of Tokyo, IPMU), K. Murase, S.Nagataki (YICP), S.Inoue (NAOJ), T.Yamamoto (Konan Univ.) Collaborators:

2. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 20082 Cosmic-ray spectrum Globally power-law spectrum Knee SNRs for energetics Ankle (dip) GCR/EGCR transition ? Pair creation dip ? Extragalactic cosmic-rays Active Galactic Nuclei (AGNs) Gamma-ray bursts (GRBs) Magneters, colliding galaxies,.. Second Knee Hypernovae (Gal/EG) ? GCR/EGCR transition ? GZK steepening Composition Maximum acceleration energy Flux [m -2 sr -1 s -1 GeV -1 ] Energy [eV] Knee Second-Knee Ankle (dip) E -2.7 Galactic EG G or EG ? LHC max Highly isotropic distribution

3. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 20083 UHECR-AGN Positional Correlation The collaboration pointed out that Extragalactic/Galactic magnetic fields are sufficiently weak Protons are dominated in highest energy cosmic-rays Spatial distribution of UHECR sources corresponds to that of nearby matter distribution (especially supergalactic plane) 2 events around Cen A, the nearest radio loud AGN “ hole ” around Virgo cluster Positional correlation between highest energy events and nearby extragalactic objects ( Pierre Auger Collaboration 2007) Cen A Supergalactic plane Pierre Auger Observatory Argentina (35.2 o S, 69.5 o W) Mean altitude: 1400m Exposure: 9000km 2 sr yr Angular resolution: less than 1 o Uncertainty in the energy scale: ~30% E>57EeV, z<0.018 (75Mpc),  =3.1 o Start charged particle astronomy

4. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 20084 Charged particle (UHECR) astronomy Statistical approaches --- large-scale and/or small-scale anisotropy Auto-correlation of events  the number density of UHECR sources (Blasi & De Marco 2004, Kacheliess & Semikoz 2005, HT & Sato 2006,2007) Cross-correlation  What type of objects is UHECR source ? (Cuoco et al. 2007) Direct approaches --- small-scale anisotropy (AGASA collab.:Takeda et al. 1999) Small-scale anisotropy  the position of each UHECR source (HT & Sato 2007)  UHECR spectrum of each source (Blasi & De Marco 2004) What is understood about the nature and origin of UHECRs from their arrival direction distribution ? We have discussed the possibility of the charged particle astronomy before the Auger results using simulations taking into account UHECR source distribution and intervening magnetic fields which reflects the local universe actually observed.

5. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 20085 Nearby universe ( d<100Mpc ) If UHECR sources are astrophysical objects, UHECR arrival distribution should reflect nearby matter distribution and magnetic field distribution. Nearby universe is not uniform Perseus Virgo Centaurus Hydra A3627, Pavo ( IRAS PSCz Catalog: Saunders et al. 2000 )

6. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 20086 Our models of UHECR source distribution and EGMF Source distribution model Galaxies selected randomly from the modified IRAS catalog with several source number densities. EGMF model B ∝  m   ∝  L  Magnetic field is normalized as 0.0, 0.1, 0.4  G in the center of Virgo Cluster, based on observations. IRAS galaxies Nearby matter distribution are constructed from IRAS PSCz catalog Galaxies in the IRAS mask are assumed to be isotropic distribution. ( Takami et al. 2006 ) (IRAS PSCz Catalog :d<100Mpc ) 0 2 4 For B=0.1  G (100Mpc propagation of protons with 10 20 eV)

7. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 20087 Calculation of the arrival distribution 1. Source distribution and extragalactic magnetic field are assumed. 2. UHECRs (protons) are propagated from the sources to the Earth taking energy-loss processes and the magnetic field into account. 3. UHECR arrival distribution can be simulated. 4. Comparing the simulated arrival distribution and the corresponding source distribution, the positional correlation is investigated. Investigate the positional correlation in simulation This study has been performed before Auger result. Energy-loss processes Photopion production Bethe-Heitler pair creation Adiabatic energy-loss

8. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 20088 GZK Mechanism (photopion production) Cosmic-rays above 10 20 eV cannot be observed at the Earth p CMB   e e+e+ ++ ++  e e+e+ np Highest energy cosmic-rays can unveil nearby universe only within 100Mpc E>6x10 19 eV ( Berezinsky 2007 )( HT+ 2007 )

9. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 20089 An example of the arrival distribution (n s ~10 -5 Mpc -3 ) Small-scale anisotropy The arrival distribution predicted from the source distribution shown below. Small-scale anisotropy is predicted in the directions of nearby sources 3000 events even if EGMF is considered.

10. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200810 Another example of the arrival distribution (n s ~10 -5 Mpc -3 ) The arrival distribution predicted from different source distribution from that last page, but the same source number density. Predicted anisotropy is dependent on source distribution

11. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200811 Arrival distribution of UHE protons above 10 19.8 eV 200 event detection finds several strong event clusters The arrival distribution with 500 events traces nearby source distribution as event clusters If n s is larger than 10 -5 Mpc -3, more event detection is required for unveiling 10 -5 Mpc -3 Auger 5yr of all the sky A demonstration in the case of no EGMF ( HT & Sato 2007 )

12. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200812 Arrival distributions of UHE protons above 10 19.8 eV Event clusters can be observed sufficiently although clustering signals become weak. The positional correlation can be also observed. Including EGMF ( HT & Sato 2007 )

13. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200813 Spatial Correlation : correlation value   1 : perfect correlation 0 : no correlation -1: perfect anti-correlation Errors finite number of events  converges to some number of events, which is interpreted as the number to unveil the source distribution. The number is dependent on the source number density. 10 -4 Mpc -3 :O(1000) events 10 -5 Mpc -3 :500 events for E>10 19.8 eV 2 o x2 o The correlation between UHECR arrival distribution and source distributions within 100Mpc. ( HT & Sato 2007 )

14. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200814 Spatial Correlation : correlation value  The converging values are different between source distribution with the same source number density. But, the numbers of events that  starts to converge are almost unchanged in 100 source distribution. 2 o x2 o We calculate the averages and variances of the  between 100 source distribution ( HT & Sato 2007 )

15. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200815 Models of Galacitc magnetic field Magnetic field in Galactic disk: Bisymmetric(BSS) or Axisymmetric(ASS) BSS has field reversals, while ASS does not Magnetic field in Galactic halo: much less known Spiral field with exponential decay in the z direction Classified by parity about Galactic plane ： symmetric(S) or anti-symmetric(A) A dipole field at Galactic center is also assumed (Alvarez-Muniz & Stanev 2006) Parity=A

16. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200816 Deflection angles of protons with 10 19.8 eV in GMF The positional correlation is lost in the direction of the Galactic center due to strong deflections. In the direction of the Galactic anti-center, the BSS models predicts smaller deflections than the ASS models. Thus, the northern observatories (such as Telescope Array) have an important role for correlation studies. A blue region is toward Cen A. What deflection angles do the arriving protons experience ? ( HT & Sato 2007 )

17. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200817 Deflection angles of protons with 10 19.8 eV in GMF Several parameters in the GMF models are changed in the consistency with observations The deflection angles can be 1-3 o in the direction of the Galactic anti-center UHECR Observatories in the terrestrial northern hemisphere are suitable for positional correlation studies !!  Telescope Array

18. Accelerators in the Universe @ KEK, Tsukuba Mar. 14, 200818 Summary We have investigated the possibility of the charged particle astronomy before the Auger results using simulations including realistic models of UHECR source distribution and EGMF. 500 and O(1000) event detections above 10 19.8 eV can unveil the local distribution of UHECR sources for 10 -5 and 10 -4 Mpc -3, respectively even if EGMF is considered. Galactic magnetic field contributes to the deflection of UHE protons to some extent. Due to the GMF, UHECR observatories in the northern hemisphere are favored for positional correlation studies.