High-energy neutrinos from extragalactic cosmic-ray sources

1. High-energy neutrinos from extragalactic cosmic-ray sources Kohta Murase (Center for Cosmology and AstroParticle Physics, Ohio State University, USA) NOW 2010

2. Outline Overview of HE ns from extragalactic sources • Gamma-ray bursts • Active galactic nuclei & clusters of galaxies • Newly born magnetars • n emission from sources of UHE nuclei

3. Neutrinos as a Messenger Purposes: • Origin of cosmic rays (CRs) • Source properties (jet contents, magnetic field etc.) • Clues to acceleration mechanisms GeV-TeV gamma-ray obs.: ・attenuation in sources and/or CMB/CIB ・ contamination by leptonic emission HE-neutrino obs. (>0.1TeV): ・more direct probe ・ neutrino physics (e.g., oscillation) • Neutrinos produced outside a source (e.g., cosmogenic) (->Stanev, Olinto) • Neutrinos produced inside a source • In this talk, we focus on the latter

4. Extragalactic Cosmic-Ray Accelerators magentars UHECR source candidates The most extreme objects! Magnetars GRB The strongest mag. fields B ~ 1015 G B AGN jet GRBs The brightest explosion EGRB~1051ergs clusters AGN The most massive BH MBH~106-9Msun r Hillas condition E < e B r b E>1020eV, Z=1 → LB≡eBL > 1047.5 erg/s G12b-1 Clusters The largest grav. obj. rvir ~ a few Mpc

5. Gamma-Ray Bursts

6. (Long) Gamma-Ray Bursts • The most violent phenomena in the universe (Lg~1051-52 ergs s-1) • Cosmological events (z~1-3) • ~1000 per year (⇔ ~ 5 yr-1 Gpc-3 @ z~1) • Relativistic jet (G~300; Eg ~ 1051 ergs ~ 0.01 Eg,iso, qjet ~ 0.1 rad) • Related to the death of massive stars (association with SNe Ic) variability~ ms Luminosity Afterglow Prompt (GRB) X-ray、optical、radio Gamma-ray～300 keV Duration～10-103s Time 10-102s 103-104s

7. Prompt emission PeV ν, GeV-TeV γ (Waxman & Bahcall 97 PRL) (KM et al. 06 ApJL) Meszaros (2001) Orphan emission TeV ν, no γ (Meszaros & Waxman 01 PRL) (Razzaque et al. 03 PRL) (Ando & Beacom 95 PRL) • emission radius ~ 1013-1015.5 cm • mildly relativistic shocks • magnetic field ~102-105G

8. Basics of Neutrino Emission Photon Spectrum (observed) CR Spectrum (Fermi mechanism) Key parameter CR loading εγ2N(εγ) εp2N(εp) 2-β~-0 2-p~0 EHECR≡εp2N(εp) ~εγ,pk2N(εγ,pk) 2-α~1.0 total ECR~20EHECR εp εγ ~ΓGeV 1018.5eV 1020.5eV εγ,pk~300 keV εmax Photomeson Production Δ-resonance at Δ-resonance εp εγ ~ 0.3 Γ2 GeV2 εpb~ 0.15 GeV mpc2 Γ2/εγ,pk ~ 50 PeV multi-pion production Photomeson production efficiency ~ effective optical depth for pγ process fpγ ~ 0.2 nγσpγ (r/Γ) (in proton rest frame)

9. Meson Spectrum pion energy επ~ 0.2 εp break energy επb~ 0.07 GeV2 Γ2/εγ,pk ~ 10 PeV επ2N(επ) α-1~0 ~fpγEHECR β-1~1 meson cooling before decay (meson cooling time) ~ (meson life time) → break energy in neutrino spectra α-3~-2.0 επ επｂ επsyn meson & muon decay Neutrino Spectrum “Waxman-Bahcall” type spectrum(Waxman & Bahcall 97 PRL) εν2N(εν) α-1~0 β-1~1 α-3~-2.0 • neutrino energy εν~ 0.25 επ ~0.05 εp • ν lower break energy ενb ~ 2.5 PeV • ν higherbreak energy ενπsyn ~ 25 PeV εν ενb ενμsyn ενπsyn pg process Neutrino oscillation No loss (Kashti & Waxman 05 PRL) High εν Loss limit

10. GRB Prompt Event rates by IceCube for 1 GRB @ z~1 ~ 10-4-10-2 → Cumulation of many GRBs (time and space coincidence) ●Meson production efficiency is rather uncertain mainly due to r and G ●~0.1-10 events/yr by IceCube (w. moderate CR loading) ●Testable case: GRB-UHECR hypothesis/Hadronic model for Fermi GRBsIceCube is constraining optimistic cases (Becker’s talk, Kappes arXiv:1007.4629) see also Dermer & Atoyan 03 PRL Guetta et al. 04 APh Becker et al. 06 APh KM & Nagataki, PRD, 73, 063002(2006) Γ=102.5, Ug=UB CR loading parameter ΕHECR ≡εp2 N(εp) high CR loading EHECR ~ 2.5 EGRBg (Up=50Ug) Set A - r~1013-14.5cm moderate CR loading EHECR ~ 0.5 EGRBg (Up=10Ug) Set B - r~1014-15.5cm

11. Alternative Scenario? • Internal shock model has problems in explaining observations • Prompt emission may be quasi-thermal rather than nonthermal (e.g., Thompson 94, Rees & Meszaros 05, Ioka, KM+ 07) • g-ray emission from tT=nesT(r/G)~1-10 ⇔ tpp~ 0.1-1 KM, PRD(R), 78, 101302(2008) Wang & Dai, ApJL, 691, L67 (2009) Γ=102.5, Ug=UB • GeV-TeV neutrinos due to pp • Efficiency is almost fixed • Detectable for smaller EHECR • Detectable even if proton • acceleration is inefficient • UHECRs are not produced pp pg EHECR=1051 erg

12. Early AfterglowsEeV ν, GeV-TeV γ(KM & Nagataki 06 PRL)(Dermer 07 ApJ)(KM 07 PRD) Meszaros (2001) Classical AfterglowsExternal Shock ModelEeV ν, GeV-TeV γ (Waxman & Bahcall 00 ApJ)(Dai & Lu 01 A&A)(Dermer 02 ApJ) • emission radius ~ 1016-1017cm • mildly relativistic reverse shock • & ultra-relativistic forward shock • magnetic field ~0.1-100 G

13. GRB Early Afterglow • Afterglows are explained by the external shock model • Proton acceleration is possible during afterglows analogous to in SNRs • Many GRBs accompany energetic flares during afterglows KM, PRD, 76, 123001 (2007) KM & Nagataki, PRL, 97, 051101 (2006) Late IS protons + flare x rays (normalized by 10% of UHECR budget) ES protons + ES opt-x rays Stellar Wind Medium (normalized by UHECR budget) ES protons + ES opt-x rays Inter Stellar Medium (normalized by UHECR budget) • Flares – efficient for meson production (fpg ~ 1-10) and detectable • ES – not easy to be seen by both neutrinos and gamma rays

14. Active Galactic NucleiandClusters of Galaxies

15. Active Galactic Nuclei • Super-massive black holes (M~106-9 Msun) • Accretion onto a BH (accretion disk) and relativistic jets (G~3-30) • Beamed nonthermal emission from inner jets -> blazar emission • AGN w. powerful jets -> radio galaxies (Fanaroff-Riley I&II) • ~1% of AGN have hot spots as well as lobes (Fanaroff Riley II) jet BH accretiondisk dust torus

16. CR and n Production in AGN Inner jet (blazar; FRI/II)(c.f. prompt) r ~ 1016-1017 cm B ~ 0.1-100 G Emax ~ Epg <~ 1017-20 eV neutron conversion? e.g., Biermann & Stritmatter 87 ApJ Mannheim+ 92 A&A Atoyan & Dermer 01 PRL Hot spot, Cocoon (FRII)(c.f. afterglow) r ~ 1021 cm B ~ 1　mG r ~ 1022 cm B ~ 0.1 mG?? Emax ~ Eesc ~ 1020-21 eV e.g., Biermann & Stritmatter 87 ApJ Takahara 90 PTP Rachen & Biermann 93 A&A Berezhko 08 ApJL ＊Core (disc/vicinity of BH)(c.f. orphan) optimistic cases (no UHECRs) Stecker+ 91 PRL, Protheroe & Szabo 92 PRL

17. Neutrinos and Gamma Rays from Blazars Neutrino spectrum Observed Photon Spectrum X-ray IR,optical GeV γ TeV γ Low-peak BL Lac Low-peak High-peak BL Lac High-peak Mucke et al. 02 Mucke+ 03 APh HE • Lower-peak blazars tend to have larger luminosities • Lower-peak blazars → efficient ν (and g) production (~ EeV neutrinos) (On the other hand, UHECR survival is more difficult due to pg)

18. Contd. HE emission can be explained by the hadronic model as well as leptonic model (e.g., Mannheim 93, Aharonian 02, Mucke+ 03) This scenario requires high CR loading, LCR >~ Lrad Jet+Disk jet Jet only Nm ~ 10-3 Nm ~ 0.1-0.4 Atoyan & Dermer 01 PRL Atoyan & Dermer 03 ApJ ns from blazars may be seen by seed photons from acc. disc(but UHECRs are depleted c.f. GRB flares)

19. AGN Jet Becker 06 PhR KM 08 AIPC Blazar-max. jet (Mannheim+ 01) FRII jet (Becker+05) Core (Stecker 05) BL Lac jet (Mucke+ 03) • Various models from different motivations • Core/Blazar-max. (norm. @ MeV/>0.1GeV) are being constrained • Norm. by UHECRs for typical BL Lacs → < 0.1-1 events/yr • But we will be in the interesting stage

20. Cen A (Non-Blazar) (Biermann’s talk) • Cen A: nearest AGN (FRI) @ ~3 Mpc • Apparently correlated with UHECRs observed by Auger • UHECR source? (e.g., Gorbunov+ 08, Sigl 09, Hardcastle 09, Gopal-Krishna+ 10) • Acc. sites • Core/inner jet • Possible hot spots • Lobes • But ns from inner jets are off-axis emission • pg in core • pp in extended high-density region • → < a few events/yr • (Cuoco&Hannestad 08 PRD • Kachelriess+ 09 NJP 09) • But, then Cen A should be particular • (Koers & Tinyakov 08 PRD ) Kachelriess+, NJP, 76, 123001 (2009)

21. AGN and Clusters of Galaxies • Clusters of galaxies contain AGN • The largest gravitationally bounded objects • (M~1014-15 Msun, r ~ Mpc) • Cosmic-ray storage room (AGN, Galaxies) • Structure formation shocks (matter accretion, cluster mergers) CRs interact with intracluster gas via pp (Berezinsky+97 ApJ, Colafransesco & Blasi 98 APh) CRs interact with rad. field via pg (De Marco+ 06 PRD, Kotera, Allard, KM+ 09 ApJ) >30 PeV CRs lead to >PeV ns

22. AGN and Clusters KM, Inoue, & Nagataki, ApJL, 689, L105 (2008) Kotera+, ApJ, 892, 391 (2009) pp pg all the flavors Eb=1017.5 eV • Norm. by HECRs above 1017.5 eV → a few events/yr (>0.1PeV) • gs are cascaded ⇔ can be consistent with Fermi g-ray bkg.

23. Newly Born Magnetars

24. Magnetars • Neutron stars with the strongest magnetic fields (B~1015 G>1012G) • Giant flares (Eflare~1044-46 erg) • Slow rotation at present (period ~5-10 s) but maybe fast rotation at birth (period ~ ms) • Birth rate may be ~ 10 ％ of core-collapse SN rate Corr. w. spiral galaxies → magnetar or GRB? Ghisellini+ 08 MNRAS, Takami+09 JCAP

25. n Production in Fast-Rotating Magnetars • UHECR acc. may occur in a cavity ~hrs after the birth (Arons 03 ApJ) • Surrounded by stellar envelope • Accelerated CRs interact with envelope and rad. Field → meson production • Escape of UHECRs？ e.g., puncturing envelope by jets → A fraction of CRs may produce mesons in jets as in GRBs (possible) jet envelope shock cavity wind NS naturally expected in the magnetar-UHECR scenario

26. Fast-Rotating Magnetars • Expected muon-event rate ~ 1-10 events/yr • Rate detecting >1 ns → ~ 0.1 yr-1 (useful for n alerts) KM, Meszaros, & Zhang, PRD, 79, 103001 (2009) Detectable for D<5Mpc Time scale ~ day soft-hard-soft time-evolution Probe of the magnetar birth

27. Neutrinos from Sources of UHE Nuclei

28. Proton or Nuclei? • HiRes/TA -> proton composition Auger -> UHECRs are largely nuclei • Hillas cond.,E>1020 eV, Z=26 → LB > 1043.5 erg/s (G/3)2b-1 Much dimmer sources are allowed as UHECR sources • Survival from photodisintegration (tAg~ngsAg (r/G) < 1) Photon and matter density should be small enough • One can build scenarios where UHE nuclei can survive GRB AGN Clusters Then, what is the consequence for detectability of neutrinos? (KM+ 08 PRD, Wang+ 08 ApJ) (e.g., Pe’er, KM, & Meszaros 09 PRD, Gopal-Krishna+ 10 ApJ) (Inoue+ 07, see also Kotera, Allard, KM+ 09, ApJ)

29. Landmarks from UHE Proton Sources Waxman-Bahcall landmarks (Waxman & Bahcall 98 PRD) reasonable bounds of cumulative ns from UHECR sources assumption： UHECR spectrum N(ep) ∝ep-2 meson production efficiency fpg (< 1) → 1 “formal” limit (fpg ~ 0.2 nγσpγ (r/Γ)) nflux en2 N (en) ~ 0.25 fpgep2 N(ep) → (0.6-3)×10-8 GeV cm-2 s-1 sr-1 Most theoretical predictions lieunder WB landmarks IceCube reaches WB landmarks below MPR landmarks

30. Landmarks from UHE Nuclei Sources Nucleus-survival requirement tAg ~ ng sAg (r/G) < 1 res. approx. → fmes ~ (0.2/A) ng A spg (r/G) ~ tAg (0.2 spg/sAg) < 10-3 KM & Beacom, PRD, 81, 123001 (2010) fAg=kAgtAg < 1 (most conservative) en2 N (en)~0.25 fmes e2 N(e) < (0.4-2)×10-9 GeV cm-2 s-1 sr-1 *non-applicable to non-UHECR sources (e.g., KM+ 08 for exception)

31. Summary ns are expected for very powerful extragalactic CR sources Various possibilities, of course many uncertainties Sources may be seen if we are lucky -> big impacts! Some of the scenarios seem testable in the near future • GRB prompt w. UHECR hypothesis (←CR loading must be large)Hadronic models for Fermi GRBs, flares… • AGNblazars in the hadronic model, flares of GeV blazars, clusters of galaxies, specific models for Cen A… • Magnetar Especially for UHECR sources, if UHE nuclei such as UHE iron ubiquitously survive in sources, Agns would be difficult to see by IceCube

32. Grazie!Thanks for organizers