High Energy Neutrinos from Astrophysical Sources Dmitry Semikoz UCLA, Los Angeles & INR, Moscow
Overview: • Introduction: cosmic rays, gamma-rays and neutrinos • Diffuse neutrino fluxes • Neutrinos from UHECR (Friday, F.Halzen , G.Miele) • Neutrinos from AGN • Most probable point-like neutrino sources • AGN • Galaxy center • Microquasars • SuperNova high energy E>TeV neutrinos • GRB (Friday, P.Meszaros) • Conclusion
Conditions required for production of high energy neutrinos in astrophysical sources: • Acceleration of charged particles (protons or nuclei) to high energies E>1015 eV • Accelerated particles should lose energy through pion production or neutron decay • Obey gamma-ray and neutrino flux limits
Neutrinos from pion production n p Conclusion: photon and neutrino fluxes are connected in well-defined way. If we know one of them we can predict other:
EGRET: gamma-ray flux The high energy gamma ray detector on the Compton Gamma Ray Observatory (20 MeV - ~20 GeV)
Photon flux at E>100 MeV as measured by EGRET till 1995 Point sources The Flux of Diffuse Photons
High energy gamma ray experiments Complementary capabilities ground-based space-based ACTEASPair angular resolution good fair good duty cycle low high high area large large small field of view small large large+can reorient energy resolution good fair good, w/ smaller systematic uncertainties The next-generation ground-based and space-based experiments are well matched.
EGRET flux can consist of: • Inverse Compton scattered photons • Synchrotron photons from high energy protons • Photons from pion decay, which cascade down in intergalactic space or in source • Thus EGRET flux give just upper limit on diffuse or point source neutrino flux
Cosmic rays and AGNs Diffused flux from cosmic rays Many unresolved sources AMANDA II
GLAST: 10000 sources LAT 1st Catalog: >9000 sources possible
Only few classes of astrophysical objects are able to accelerate particles to highest energies • For neutrino production we have to look for the sources with high density of background photons or protons
Can sources accelerate protons to such high energies? AGASA data E> 1019 eV: AGNs are one of most probable sources
Neutrinos from AGN core AMANDA II J.Alvarez-Muniz and P.Mezsaros, astro-ph/0409034
Point source fluxes • Background of atmospheric neutrinos against flux of given source. Position of source given a priori. • AMANDA II 1.8 degrees resolution: 3 background 6 observed • ANTARES 0.3 degrees • ICECUBE 0.5 degrees • KM^3 0.3 degrees<
Most probable single sources- AGN • Blazars • GeV-loud • Optical depth for protons should be large: t = spg ng R>>1 Only 22 sources from 66 are GeV - loud
TeV blazars does not obey last condition • Indeed, in order TeV blazars be a neutrino sources: • = spg ng R>>1 • = sgg ng R <<1 spg = 6x10-28cm2while for TeV gamma-rays sgg = 6.65 x 10-25cm2 • CONTRADICTION!!! Except if proton background density is as high as photon one, because spp= 6x10-26cm2 This is unlikely in BL Lacs, where emission lines are absent.
Which sources ? • Blazars (angle – energy correlation) • Blazars should be GeV loud • Optical depth for protons should be large: t = spg ng R>>1 • No 100 - kpc scale jet detected (model-dependent)
Bound on blazars which can be a neutrino sources A.Neronov, D.S., 2002
Galaxy center: cosmic rays • AGASA experiment see anisotropy towards the Galactic center. • This signal can be explained by neutrons.
Galaxy center • Cosmic ray neutrons decay on the way and produce neutrinos. L.Archadoqui, H.Holdberg, F.Halzen and T.Weiler, astro-ph/0311002
Microquasars • AGN on star scales. • Protons are accelerated by shock wave up to 1016 eV • In interaction with X-ray photons from accretion disk protons produce 1-100 TeV neutrinos A.Levinson and E.Waxman, 2001 C.Distefano et al, 2002
Supernova 1987A 23 February 1987 Galactic SN • When shock came out of star it start to accelerate protons. • Up to 200 events with E>1 TeV in ICECUBE within few hours (E.Waxman and A.Loeb, astro-ph/0102317) • Extra 1000-10000 events in first year (V.Berezinsky and V.Ptuskin, 1988) • Can help to detect SN location up to 0.1 degree. (R.Tomas, D.S., G.Raffelt, M.Kachelriess and A.Dighe, hep-ph/0307050)
Conclusions • Diffuse neutrino flux can be combination of cosmic ray and AGN neutrinos. • GeV-loud blazars with high optical depth for protons are good candidates for point-like neutrino sources. • Galaxy center can be good source of neutrinos and flux can be predicted based on AGASA signal. • Galactic microquasars, GRB, galactic SN are sources of neutrinos. • We have a good chance to detect those sources with km2 detectors.