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High-energy neutrinos from extragalactic cosmic-ray sources. Kohta Murase (Center for Cosmology and AstroParticle Physics, Ohio State University, USA). NOW 2010. Outline. Overview of HE n s from extragalactic sources Gamma-ray bursts Active galactic nuclei & clusters of galaxies

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High energy neutrinos from extragalactic cosmic ray sources

High-energy neutrinos from extragalactic cosmic-ray sources

Kohta Murase

(Center for Cosmology and AstroParticle Physics,

Ohio State University, USA)

NOW 2010


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

Neutrinos as a messenger
Neutrinos as a Messenger


  • 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

High energy neutrinos from extragalactic cosmic ray sources

Extragalactic Cosmic-Ray Accelerators


UHECR source candidates

The most extreme objects!



The strongest mag. fields

B ~ 1015 G


AGN jet


The brightest explosion




The most massive BH



Hillas condition E < e B r b

E>1020eV, Z=1

→ LB≡eBL > 1047.5 erg/s G12b-1


The largest grav. obj.

rvir ~ a few Mpc

Long gamma ray bursts
(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



Prompt (GRB)


Gamma-ray~300 keV





High energy neutrinos from extragalactic cosmic ray sources

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

Basics of neutrino emission
Basics of Neutrino Emission

Photon Spectrum (observed)

CR Spectrum (Fermi mechanism)

Key parameter

CR loading








total ECR~20EHECR






εγ,pk~300 keV


Photomeson Production


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)

High energy neutrinos from extragalactic cosmic ray sources

Meson Spectrum

pion energy επ~ 0.2 εp

break energy επb~ 0.07 GeV2 Γ2/εγ,pk ~ 10 PeV





meson cooling before decay

(meson cooling time) ~ (meson life time)

→ break energy in neutrino spectra





meson & muon decay

Neutrino Spectrum

“Waxman-Bahcall” type spectrum(Waxman & Bahcall 97 PRL)





  • neutrino energy εν~ 0.25 επ ~0.05 εp

  • ν lower break energy ενb ~ 2.5 PeV

  • ν higherbreak energy ενπsyn ~ 25 PeV





pg process

Neutrino oscillation

No loss

(Kashti & Waxman 05 PRL)

High εν

Loss limit

Grb prompt
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



Set A - r~1013-14.5cm

moderate CR loading



Set B - r~1014-15.5cm

Alternative scenario
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



EHECR=1051 erg

Early afterglows eev gev tev km nagataki 06 prl dermer 07 apj km 07 prd
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

High energy neutrinos from extragalactic cosmic ray sources

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

Active galactic nuclei and clusters of galaxies

Active Galactic NucleiandClusters of Galaxies

Active galactic nuclei
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)




dust torus

Cr and n production in agn
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

Neutrinos and gamma rays from blazars
Neutrinos and Gamma Rays from Blazars

Neutrino spectrum

Observed Photon Spectrum



GeV γ

TeV γ

Low-peak BL Lac


High-peak BL Lac


Mucke et al. 02

Mucke+ 03 APh


  • 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)

High energy neutrinos from extragalactic cosmic ray sources


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 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)

Agn jet

Becker 06 PhR


Blazar-max. jet

(Mannheim+ 01)

FRII jet



(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

Cen a non blazar
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)

Agn and clusters of galaxies
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

Agn and clusters
AGN and Clusters

KM, Inoue, & Nagataki, ApJL, 689, L105 (2008)

Kotera+, ApJ, 892, 391 (2009)



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.


  • 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

N production in fast rotating magnetars
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








naturally expected in the magnetar-UHECR scenario

Fast rotating magnetars
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

Proton or nuclei
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




    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)

Landmarks from uhe proton sources
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

Landmarks from uhe nuclei sources
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)


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

Grazie thanks for organizers
Grazie!Thanks for organizers