Download High Energy Neutrino Astronomy

JUNO Workshop, IHEP, 2015/7/10
Active Galactic Nuclei
&
High Energy Neutrino Astronomy
>TeV
黎卓
北京大学
Outline
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Background: neutrino detection; sources
AGN phenomena
AGN neutrino models
constraint by gamma-ray
Conclusion
HE neutrino flux implied by UHE cosmic ray
• Neutrinos from  production
p   ( p)  N   
CR spectrum
   e   e    
• If all p energy converted to 
j 1 1 1 / H 0
  
j p 2 2 GZK / c
• Waxman-Bahcall Bound from
detected >1019eV CR flux :
dj
GeV
8

 10 
d
cm 2s sr
2
Waxman & Bahcall 1999
IceCube: KM scale
•KM3 size to detect GZK neutrino,
as well as SNR, AGN & GRB
•DUMAND, 1976-1995
•AMANDA, operation 2000
•IceCube, completed 2010
10s evts/yr for WB bound
High energy neutrino discovery
2010/5-2012/5 data:
1. EeV GZK neutrino search
•
found two at 1 PeV
2. Follow-up search: 28 evts
1. Lower E
2. Interaction vertices within
detector volume
Veto entering tracks
North
HE tracks?
3yr IC86, 37 evts, 5.7sigma
(8.4 atm muon, 6.6 atm neutrino)
South
30TeV-2PeV
E-2 PL, 1:1:1, isotropic
Diffuse neutrinos
per flavor
Harder than atmospheric events
Uncertainty: charm meson decay
Consistent with isotropic
Disfavor charm component
–which expect south 50% smaller than north
Diffuse neutrinos
Sky map, no significant spot
Also no clustering in time,
no correlation with GRB
Spectrum: best fit E-2.3
Or E-2 spectrum + PeV cutoff
•unbroken unlikely
PeV neutrino source?
• Galactic origin
– CR propagation: diffuse
– point sources (isotropic?!)
• Pulsar, SNR, PWN, micro-quasar, …
• Extragalactic origin
– p-p: CR propagation
• Star forming/starburst galaxies
• Galaxy clusters
• …
– p-: in-source
• Gamma ray bursts
• Active galactic nuclei: jets & core
• …
Stacking search
~200 GRBs
upper limit
Null results…
Gamma – neutrino connection
p   ( p)  N   
   e   e    
e   cascade radiation
 N  0
 0  
e   synch/inve rse Comp radiation
Connection:
I. neutrino -- secondary electron
II. neutrino -- secondary gamma-ray
III. neutrino -- primary proton/electron
Fermi-LAT probes neutrino origin
Whether various candidates can produce
the IceCube neutrino flux?
Galactic diffuse emission: unlikely
• Pi0 gamma-neutrino
Fermi-LAT
• Extrapolation: GeV to
PeV
– Galactic CR spectral index
-2.75
– p-p neutrino spectrum
follows CR
IC
MW diff. emis.
[Wang, LZ, Zhao 2014]
AGN property
• Compact and strong nuclear
emission
– luminosity 10^43-48 erg/s; size
<0.1pc (1pc=3.08E18cm)
• Broad band radiation spectra
FSRQ
– primarily non-thermal, F∝-α
(polarized)
– thermal in some bands (but not
from stars)
• Strong emission lines
– Widths suggest velocity up to
1E4 km/s
• Variability
BL Lac
– in continuum and emission line
flux, as well as line profile and
polarization
• Stronger X- and Gamma-ray
(than normal galaxies)
Unified model
• BH
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– 1E6~1E10 Msun
Disk
Torus
Jet
BLR
NLR
…
• Viewing angle effect
Blazar spectrum: two bumps
• Low energy bump
– Electron synchrotron
• Gamma origin
– Leptonic model
• electron IC
– Hadronic model
• Pi decay
• P-synchrtron
BL Lac 3C 66A
AGN CRneutrino
• Jet model
– CR accelerated at Jet
– Target photon:
jet+disk+BLR+torus
– Relativistic beaming;
bright
• Core model
– CR accelerated at core
region: disk or near BH
– Target: disk photon
– Isotropic emission; high
pion production efficiency
Dust torus
(IR)
Accretion disk
(UV, X)
CR
CR
Broad line region
(optical, UV)
Model uncertainty
• L~LCR*f(n,r…)
• Assumption:
– Murase+14 (jet model)
LCR=xCRLrad; ;need
xCR>100-1000
– Stecker 91,92,05,13
(core model)
L=Lx, 10%LMeV, …
Blazars in IC neutrino fields
• Blazars in the error box
of IC’s neutrinos (three
0.1-1PeV neutrinos):
[TANAMI, Krauß et al. 2014]
– six resolved +
unresolved
• can produce IC’s
neutrinos
– assuming
!!
• ANTARES does not
see neutrinos in those
fields
[ANTARES+TNAMI 2015]
Integration
Gamma – neutrino connection
p   ( p)  N   
   e   e    
e   cascade radiation
 N  0
 0  
e   synch/inve rse Comp radiation
Connection:
I. neutrino -- secondary electron
II. neutrino -- secondary gamma-ray
III. neutrino -- primary proton/electron
Flat spectrum radio quasar (FSRQ) jets
• Assume
– neutrino flux proportional to
gamma flux
– FSRQs can account for IC
neutrinos
Diffuse gamma-ray from FSRQs
derived from Fermi-LAT survey
Gamma>>neutrino flux
• Neutrino/gamma flux ratio
–
(20TeV-2PeV)/(0.1100GeV)=3.8%
• gamma (>0.1GeV) is not from
hadronic model with cascade
emission
– where the flux ratio=O(1)
– (p-synch still OK)
[Wang & LZ 15]
gamma
neutrino
[Fermi-LAT, Ajello+ 2012]
Candidate FSRQs
• apply the ratio to
individual FSRQs
• predict neutrino flux
• comparison with IC limit
• several sources in
northern sky
overpredicted
[Wang & LZ, 2015]
Stacking search
• 33 bright FSRQs
– selected based on gamma
flux
sensitivity
• Prediction/limit>10
– >30 @ northern sky
• So FSRQs can only
account for <10% (<3%)
IC neutrinos
prediction
upper limit
[Wang & LZ, 2015]
Conclusion & discussion
• IceCube neutrino origin
– Fermi-LAT observations disfavor
• disfavor Galactic origin (diffuse emission & point sources), GRB, &
AGN (FSRQ & BL Lac) jet
• favor star forming/starburst galaxies
– Current stacking limit cannot constrain AGN core model yet
• Stack more AGN (how many?)
• AGN jet still possible to be UHE CR sources
– AGN neutrinos is a few% diffuse neutrinos; and f~a few%,
–  CR power maybe consistent with observed UHECR flux
Starburst galaxies: II
Fermi-LAT, Ackermann+12
Starburst galaxies: II
• Local-universe gamma-ray emissivity
• Redshift-integrated gamma-ray intensity
• Neutrino flux and spectrum:
– if CRs injected with ~Ep-2.2 as observed in MW
– if <100PeV CRs lose energy significantly as expected in SBs
Match both flux and spectrum by IC
IC flux = WB bound?
• Simply coincident?
• The same sources
for both >1019eV
CR and IceCube
neutrinos?
– GRBs in starbursts
Wang, Zhao & Li, 2014