Self-Consistent Model of Extragalactic Neutrino Flux from Evolving Blazar Population
- PDF / 640,132 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 82 Downloads / 154 Views
UCLEI, PARTICLES, FIELDS, GRAVITATION, AND ASTROPHYSICS
Self-Consistent Model of Extragalactic Neutrino Flux from Evolving Blazar Population A. Neronova,b and D. Semikoza, * a
APC, Université Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cité, Paris, 119 75205 France b Astronomy Department, University of Geneva, Ch. d’Écogia 16, Versoix, 1290 Switzerland *e-mail: [email protected] Received December 20, 2019; revised December 20, 2019; accepted December 25, 2019
Abstract—We study constraints on the population of neutrino emitting blazars imposed by the absence of doublets in astrophysical muon neutrino signal and z 0.3 redshift of nearest identified neutrino-emitting blazar (an order of magnitude further away than the nearest γ-ray emitting blazar). We show that in spite of the absence of correlation of neutrino arrival directions with positions of gamma-ray emitting blazars, cumulative blazar flux could explain most of astrophysical neutrino flux measured in muon neutrino channel. This is possible if the population of neutrino emitting blazars has experienced rapid positive evolution at least as (1 + z)5 at z & 1. Such a model avoids previously derived constraint on the low level of blazar contribution to extragalactic neutrino flux because gamma-ray and neutrino fluxes are dominated by different sets of blazars. Rapid evolution of neutrino emitting blazars could be explained by the fact that only rapidly evolving sub-population of blazars, which can include parts of Flat Spectrum Radio Quasar and bright BL Lac populations, are efficient neutrino sources, although their neutrino luminosity has to be systematically lower than the γ-ray luminosity. DOI: 10.1134/S1063776120050088
1. INTRODUCTION Five years after discovery [1], the origin of astrophysical neutrino signal detected in “high-energy starting events” (HESE) [2] and muon neutrino [3] channels by IceCube telescope remains uncertain. The overall flux and spectral slope of the HESE signal are consistent with the high-energy extrapolation of the gamma-ray flux detected by Fermi telescope up to the TeV band [4–8]. Given that the TeV gamma-ray flux from the sky is dominated by the emission from the Milky Way, the steep-spectrum HESE neutrino flux could well be of Galactic origin. Anisotropy pattern of the signal does not reveal strong excess toward the Galactic Plane of the type predicted by models of cosmic ray propagation in the Milky Way disk [9–11]. However, the template of Galactic neutrino signal in 100 TeV range is difficult to work out because those neutrinos are produced by cosmic rays with energies in 1–10 PeV range which do not propagate through the interstellar medium in the same way as 10 GeV cosmic rays which produce GeV gamma-ray emission [4, 12]. Neutrino signal at energies higher than several hundred TeV sampled from the Northern hemisphere with muon neutrinos reveals harder spectrum compared to that of the HESE neutrino flux [3, 13]. This
hardening could be due to the presence of extragalactic component of
Data Loading...
