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Astrophysical Sources of UHECRs

Astrophysical Sources of UHECRs. Tom Jones University of Minnesota. Outline. Observational constraints Basic physical limitations on sources Some astrophysical models. All particle cosmic ray spectrum. UHECR. LHC. ppCM ZeV. Nagano & Watson 00. Spectrum below ~100EeV pretty well known.

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Astrophysical Sources of UHECRs

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  1. Astrophysical Sources of UHECRs Tom Jones University of Minnesota KAW4, Daejeon

  2. Outline • Observational constraints • Basic physical limitations on sources • Some astrophysical models KAW4, Daejeon

  3. All particle cosmic ray spectrum UHECR KAW4, Daejeon LHC ppCM ZeV Nagano & Watson 00

  4. Spectrum below ~100EeV pretty well known KAW4, Daejeon

  5. UHECR Composition: could be almost all p Best Fit: 80% p; QGSJet 60% p; SIBYLL Abbasi etal, ApJ 2005 KAW4, Daejeon

  6. Propagation Issue 1: Protons > 0.1 ZeV severely limited by energy losses on CMB photons (Greisen-Zatsepin-Kuzmin; GZK)1,2 Photo-pair production Photo-pion production Path limit:  is cross section  is fractional energy loss 1Assuming ‘standard physics’ 2 Also an accelerator issue using local photon field KAW4, Daejeon

  7. Resulting Propagation Limits Against CMB Pair losses Pion losses Conditions matched to look back time, adiabatic losses included Concordance CDM ‘GZK sphere’ KAW4, Daejeon

  8. Do we see the GZK feature? HiRes vs AGASA Number of events: EEeV > 10: ~ 103 EEeV > 40: ~ 100 EEeV > 100: ~ 10 1 EeV 1 ZeV Abu-Zayyad etal, APh, 18, 237 (2002) KAW4, Daejeon

  9. Small statistics: photo-pion losses are discrete: GZK feature not yet confirmable De Marco, Blasi & Olinto (APh, 20, 53 (2003)) KAW4, Daejeon

  10. Propagation issue 2: What do arrival directions tell us About the sources? >Nearly isotropic with perhaps some clustering and/or correlations with ‘interesting’ astrophysical objects KAW4, Daejeon

  11. Auger: Sky Map of Data set Auger latitude= -36. Always sees South with limited coverage in North. Mantsch etal KAW4, Daejeon

  12. AGASA Small Scale Clustering for E >4x1019eV • Isotropic in large scale  Extra-Galactic • But, Clusters in small scale (Δθ<2.5deg) • 1triplet and 6 doublets (2.0 doublets are expected from random) • One doublet  triplet(>3.9x1019eV) and a new doublet(<2.6deg) KAW4, Daejeon

  13. BL Lac /UHECR Cross-correlations? logE>19.5 Gorbunov etal 2004 KAW4, Daejeon

  14. KAW4, Daejeon

  15. Deflection of Protons >41019eV(< 100 Mpc) 0o 360o Dolag etal 2003 KAW4, Daejeon

  16. Astrophysical Source Energetics: Local energy density in 100 EeV CRs u~4pJ/c~3x10-22 J/m3~3x10-21 erg/cm3 tloss~3x108yr, so e~u/tloss~10-37 W/m3 e~3x1044 erg/Mpc3/yr Roughly equivalent to ~ 1 ‘AGN’ inside 100 Mpc (~2x10-7 Mpc-3) Or Cosmic GRB rate ignoring evolution Perhaps event cluster statistics gives a space density [Blasi & De Marco 2004] ~ 10-5 Mpc-3 from AGASA data KAW4, Daejeon

  17. Some Astrophysical Accelerator Issues • How particles of such extreme energy (~1021 eV = 1 ZeV) can be accelerated and escape; i.e, what can make a “Zevatron”? • How to match the GZK feature (tflight < 108yr above ~100 EeV) if it exists or not (source spectrum) • How to account for an essentially isotropic distribution of detections (sources & propagation), maybe with some correlations and clustering KAW4, Daejeon

  18. Emax:Some Standard Estimates for an Accelerator • Containment: rg = (E)/(ZeB) < R • E < ZeBR • Unipolar inductor: E<ZeBR (WR/c)~ba ZeBR • Diffusive shock acceleration (DSA) (nonrelativistic): • tacc ~ 10 k/(u2s) < R/uswith k > rg c • E < bsZeBR • Relativistic shock DSA (analogous argument): • E < GsZeBR • All lead roughly to (Hillas): • E < 0.9 bG Z BGauss Rpc ZeV KAW4, Daejeon

  19. “Hillas Plot” for some plausible accelerators (after Hillas 1984) KAW4, Daejeon

  20. Those estimates based on simple field models Magnetic field amplification? For example, in shocks (Bell & Lucek 2000) Resonant wave instability: KAW4, Daejeon

  21. KAW4, Daejeon

  22. Photo-pion production off Blackbody radiation ng =20 T3cm-3; Eg = 3.5x10-4T eV Settingtg > R/c gives R < 1/(20asT3) Near threshold, E > 8x1019T-1 eV, s ~ 10-28cm-2; a ~ 0.1 So propagation distance limited by max(R, ctacc) < 2.5x1026 cm (2.7/T)3 cm Compact high luminosity accelerators probably eliminated: *AGN (T~105K), R<0.3 AU for E>1014 eV *Near young neutron star (T ~ 3x107K), R<25 km for E>3x1012eV KAW4, Daejeon

  23. Some Models: Radio Galaxy Jet Terminal Shock • (e.g., Rachen & Biermann 1993) • us > 0.1c; ba>0.1 • R ~ 10 kpc • B ~ 10-5-4 G • Hillas constraint applied to DSA give E ~ 1 ZeV;tacc > 105 yr • Synchrotron & photo-pion losses give comparable limit • Shear layer of relativistic jet(eg, Ostrowski 2002, Rieger & Duffy 2004) • (similar to DSA, except boostDE/E ~ Gj, so can be quick • in principle. Escape still limits to Hillas constraint. • RGs rare in the local universe, so isotropy from RGs inside GZK sphere requires nanoGauss intergalactic and/or 100 nanoGauss galactic halo magnetic fields to deflect arrival directions. • Jet proton content uncertain KAW4, Daejeon

  24. BL Lac Jets Possible correlation with BL Lacs relativistic jets with  ~ 10 beamed our way Local BLL density small, so same isotropy concerns already mentioned If sources outside GZK sphere, then `X-bursts’, ‘uhecrons’ ? (‘liberated’ superheavies, products that avoid or delay GZK) (Albuquerque etal 1998; Biermann & Frampton 2005) KAW4, Daejeon

  25. Cosmic structure shocks Kang, Rachen & Biermann 1997 shocks thermal emission ~20Mpc box Shock surfaces Thermal Emissivity Cluster shocks are big (~ Mpc), moderately fast (~103km/sec), but B is weak (~< mG), so E < few EeV by various arguments (e.g., Norman, Melrose & Achterberg 1995; Ostrowski & Siemieniec-Ozieblo 2002) KAW4, Daejeon

  26. Larger shocks: sheets, filaments & ‘superclusters’ R ~ 10s of Mpc us ~ few 102 km/sec B ~ 10-9-10-7 G? E ~ 100 EeV ? Not likely 25h-1 Mpc box Ryu, Kang, Hallman & Jones 2003 KAW4, Daejeon

  27. KAW4, Daejeon

  28. Gamma Ray Bursts: e.g., Waxman 1995, 2000; Vietri 1995 Ultrarelativistic shocks in fireballs (jets): ~1052-53 erg G>300, with internal shocks from flow variations Waxman 1995, 1999: DSA at internal shocks; R < 1016 cm If B in equipartition with radiation, B~104 Gauss E < ZeBR ~ 1020 eV (photopion losses not as restrictive, But synchrotron losses should limit E<1019 eV) Shock/Proton efficiency? Evolution constraints KAW4, Daejeon

  29. GRB Blast Wave Model e.g., Vietri 1995; Gallant & Achterberg 1999; Vietri, De Marco & Guetta 2003 • If in ISM, insufficient time to reach UHE (G & A): • E < 5x1015 BmG (E52h3/n0)1/3 eV, • h= E /Mc2 • If in a Pulsar Wind Bubble, then • B ~ 0.1-10 G for R ~ 1016 cm • E < 1020h32 xiW eV, • W is spin down luminosity, • xi is the proton mass fraction • Energetics: If no evolution, theneGRB ~ eUHE KAW4, Daejeon

  30. Young Magnetar Winds Arons (ApJ, 589, 871, 2003) • Winds avoid large magnetospheric energy losses • (Blasi, Epstein & Olinto 2000) • F~ 3x1022m33 (W4)2V available magnetic rotator voltage • Ion return current sheet may experience ~10% ofF • Wind can carry substantial fraction of spindown energy • Spin down time ~ 5 I45/(m33W4)2minutes • Ions may ‘surf’ the wind • A fast magnetar birth rate ~ 10-5 /yr/galaxy • & 10% efficiency for UHECR • accounts for energetics • Injection spectrum ~ E-1 • steepening to E-2 if early GR spindown • Is the wind dissipated in ejecta? KAW4, Daejeon

  31. Summary: • UHECR spectrum extends at least beyond 100 EeV • Probably extragalactic & ‘light’ hadrons • Serious constraints on source physics and spatial distributions • Proposed astrophysical source models numerous • Common themes: • Strong, very fast shocks (relativistic) • Strong shear (relativistic) • Rapidly rotating, magnetized objects/relativistic winds • All models require some ‘faith’ to get > ZeV, enough flux • New data (CR spectrum, isotropy, composition,  & ) • should trim/refine the list. KAW4, Daejeon

  32. The End KAW4, Daejeon

  33. Structure Shock Mach number distribution by upstream phase Hot: T > 107 K WHIM 105 K< T < 107 K Regions surrounding Clusters contain Moderately strong Shocks (unvirialized) ‘External’ shocks Hallman (UMN PhD thesis (2004)) KAW4, Daejeon

  34. Energy Extracted by CRs Could be Substantial Shock dissipation near Clusters (R < 1 h-1 Mpc) Triangles: Thermal Squares: CRs (nonlinear DSA Model from Ryu etal 2003) Hallman (UMN PhD thesis (2004)) KAW4, Daejeon

  35. Can Structure Shocks Accelerate UHECRs? With standard diffusion assumptions (i.e, Bohm), DSA just too slow with likely fields to beat photopion losses above GZK Setting a <  gives or KAW4, Daejeon

  36. Quasi-Perpendicular Shocks Might Beat This (?) Kang, Rachen & Biermann (MNRAS, 286, 257 (1998)) If MHD turbulence is weak ( =  rg >> rg) and B perp to shock normal, then, cross-field diffusion controls DSA (Jokipii, (ApJ, 313, 842 ( 1987)):   perp  (1/2) par, where < (c/us) a ~ (1/ 2) a (Bohm) << a (Bohm) Additional constraints: diffusion along B (escape) Ostrowski & Siemieniec-Ozieblo (A&A 386, 829 (2002), Or requiring rg < Rshock. Both basically return the Hillas constraint, so B » G (clusters) B » 100 nG (filaments) KAW4, Daejeon

  37. Turbulent, 2nd Order Acceleration Very likely present, but generally slower than DSA For strong Alfvenic turbulence, compared to strong shock DSA a(2nd order) ~ (us/vA)2 a(DSA) » a(DSA) KAW4, Daejeon

  38. HiRes Collab ‘02 KAW4, Daejeon

  39. ‘Dead Quasars’ Boldt & Ghosh 1999 Levinson 2000 • Quasars rare today • However, most galaxies host SMBH • ‘Dead’ or ‘underfed’ AGNs • B & G estimate > ten 109 Msun SMBH within 50 Mpc • ~ 2x10-5 Mpc-3; L ~ 1042 erg/sec • Model: Extraction of rotational energy • via BZ-induced magnetic field: emf ~ 1021 V (109 Msun) • Curvature radiation reduces limit > order of magnitude • Details not available KAW4, Daejeon

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