Transcript スライド 1 - Istituto Nazionale di Fisica Nucleare

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 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
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)
   CMB/CIB  e   e
•Neutrinos produced outside a source (e.g., cosmogenic) (->Stanev, Olinto)
•Neutrinos produced inside a source

In this talk, we focus on the latter
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
r
Hillas condition E < e B r b
E>1020eV, Z=1
→ LB≡eBL > 1047.5 erg/s G12 b-1
The most massive BH
MBH~106-9Msun
Clusters
The largest grav. obj.
rvir ~ a few Mpc
Gamma-Ray Bursts
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(Long) Gamma-Ray Bursts
•The most violent phenomena in the universe (L~1051-52 ergs s-1)
•Cosmological events (z~1-3)
•~1000 per year (⇔ ~ 5 yr-1 Gpc-3 @ z~1)
•Relativistic jet (G~300; E~ 1051 ergs ~ 0.01 E,iso, qjet ~ 0.1 rad)
•Related to the death of massive stars (association with SNe Ic)
Luminosity
variability~ ms
Afterglow
Prompt (GRB)
X-ray、optical、radio
Gamma-ray～300 keV
Duration～10-103s
Time
10-102s
103-104s
Meszaros (2001)
Prompt emission
Orphan emission
PeV ν, GeV-TeV γ
•emission radius ~ 1013-1015.5 cm
TeV ν, no γ
(Meszaros & Waxman 01 PRL) (Waxman & Bahcall 97 PRL) •mildly relativistic shocks
(KM et al. 06 ApJL)
•magnetic field ~102-105G
(Razzaque et al. 03 PRL)
(Ando & Beacom 95 PRL)
Basics of Neutrino Emission
Photon Spectrum (observed)
CR Spectrum (Fermi mechanism)
εp2N(εp)
Key parameter
CR loading
2-p~0
total ECR~20EHECR
EHECR≡εp2N(εp)
~εγ,pk2N(εγ,pk)
εγ2N(εγ)
2-β~-0
2-α~1.0
εp
~ΓGeV
1018.5eV 1020.5eV
εγ
εγ,pk~300 keV
εmax
Photomeson Production
p    n     p ~ 0.2
p    N    X  p ~ (0.4  0.7)
Δ-resonance

multi-pion production

(in proton rest frame)
at Δ-resonance
εp εγ ~ 0.3 Γ2 GeV2
εpb~ 0.15 GeV mpc2 Γ2/εγ,pk ~ 50 PeV
Photomeson production efficiency
~ effective optical depth for pγ process
fpγ ~ 0.2 nγσpγ (r/Γ)
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
α-3~-2.0
επ
επsyn
επｂ
meson cooling before decay
(meson cooling time) ~ (meson life time)
→ break energy in neutrino spectra
meson & muon decay π ± → μ ± + νμ ( νμ ) → e± + νe ( νe ) + νμ + νμ
Neutrino Spectrum “Waxman-Bahcall” type spectrum (Waxman & Bahcall 97 PRL)
 →   n (n )
εν2N(εν)
α-1~0
β-1~1
 → e  ne (ne )  n (n )
α-3~-2.0
εν
ενb
ενμsyn
Neutrino oscillation
ενπsyn
neutrino energy εν ~ 0.25 επ ~ 0.05 εp
•ν lower break energy ενb ~ 2.5 PeV
•ν higher break energy ενπsyn ~ 25 PeV
p process
n e : n : n   1 : 2 : 0
n e : n : n   1 : 1 : 1
(Kashti & Waxman 05 PRL)
ne : n : n  1:1.8 :1.8
No loss
High εν
Loss limit
GRB Prompt
Event rates by IceCube for 1 GRB @ z~1 ~ 10-4-10-2
→ Cumulation of many GRBs (time and space coincidence)
KM & Nagataki, PRD, 73, 063002 (2006)
Γ=102.5, U=UB
see also Dermer & Atoyan 03 PRL
Guetta et al. 04 APh
Becker et al. 06 APh
CR loading parameter
ΕHECR ≡εp2 N(εp)
high CR loading
EHECR ~ 2.5 EGRB
(Up=50U)
Set A - r~1013-14.5cm
Set B - r~1014-15.5cm
moderate CR loading
EHECR ~ 0.5 EGRB
(Up=10U)
●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
GRBs
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)
 -ray emission from T=nesT(r/G)~1-10 ⇔ pp~ 0.1-1
KM, PRD(R), 78, 101302 (2008)
Wang & Dai, ApJL, 691, L67 (2009)
Γ=102.5, U=UB
GeV-TeV neutrinos due to pp
pp
p
EHECR=1051 erg
•Efficiency is almost fixed
•Detectable for smaller EHECR
•Detectable even if proton
acceleration is inefficient
•UHECRs are not produced
Meszaros (2001)
•emission radius ~ 1016-1017cm
•mildly relativistic reverse shock
& ultra-relativistic forward shock
•magnetic field ~0.1-100 G
Early Afterglows
EeV ν, GeV-TeV γ
(KM & Nagataki 06 PRL)
(Dermer 07 ApJ)
(KM 07 PRD)
Classical Afterglows
External Shock Model
EeV ν, GeV-TeV γ
(Waxman & Bahcall 00
ApJ)
(Dai & Lu 01 A&A)
(Dermer 02 ApJ)
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 (fp ~ 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 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
accretion disk
dust torus
CR and n Production in AGN
Inner jet (blazar; FRI/II) (c.f. prompt)
r ~ 1016-1017 cm B ~ 0.1-100 G
Emax ~ Ep <~ 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 G??
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
Observed Photon Spectrum
IR,optical X-ray
GeV γ
Neutrino spectrum
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 ) production (~ EeV neutrinos)
(On the other hand, UHECR survival is more difficult due to p)
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
N ~ 0.1-0.4
N ~ 10-3
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
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
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
•p 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
•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 p
(De Marco+ 06 PRD, Kotera, Allard, KM+ 09 ApJ)
>30 PeV CRs lead to >PeV ns
AGN and Clusters
KM, Inoue, & Nagataki, ApJL, 689, L105 (2008)
Kotera+, ApJ, 892, 391 (2009)
pp
all the flavors
Eb=1017.5 eV
p
•Norm. by HECRs above 1017.5 eV → a few events/yr (>0.1PeV)
s are cascaded ⇔ can be consistent with Fermi -ray bkg.
Newly Born Magnetars
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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
n Production in Fast-Rotating Magnetars
envelope
(possible)
jet
shock
cavity
wind
NS
• 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
KM, Meszaros, & Zhang, PRD, 79, 103001 (2009)
Detectable for D<5Mpc
Time scale ~ day
soft-hard-soft time-evolution
Probe of the magnetar birth
• Expected muon-event rate ~ 1-10 events/yr
• Rate detecting >1 ns → ~ 0.1 yr-1 (useful for n alerts)
Neutrinos from Sources of
UHE 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)2 b-1
Much dimmer sources are allowed as UHECR sources
• Survival from photodisintegration (A~n sA (r/G) < 1)
Photon and matter density should be small enough
• One can build scenarios where UHE nuclei can survive
(KM+ 08 PRD, Wang+ 08 ApJ)
GRB
(e.g., Pe’er, KM, & Meszaros 09 PRD, Gopal-Krishna+ 10 ApJ)
AGN
Clusters
(Inoue+ 07, see also Kotera, Allard, KM+ 09, ApJ)
Then, what is the consequence for detectability of neutrinos?
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 fp (< 1) → 1 “formal” limit
(fp ~ 0.2 nγσpγ (r/Γ))
n flux en2 N (en) ~ 0.25 fp ep2 N(ep)
→ (0.6-3)×10-8 GeV cm-2 s-1 sr-1
Most theoretical predictions lie
under WB landmarks
IceCube reaches WB landmarks
below MPR landmarks
Landmarks from UHE Nuclei Sources
Nucleus-survival requirement A~nsA(r/G) < 1
res. approx. → fmes ~ (0.2/A) n A sp (r/G) ~ A (0.2 sp/sA) < 10-3
KM & Beacom, PRD, 81, 123001 (2010)
fAAA < 1
(most conservative)
en2 N (en)~0.25 fmes e2 N(e)
< (0.4-2)×10-9 GeV cm-2 s-1 sr1
*non-applicable to non-UHECR sources (e.g., KM+ 08 for exception)
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…
• AGN
blazars 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,
A ns would be difficult to see by IceCube
Grazie!
Thanks for organizers