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Title: THE CONTRIBUTION OF FERMI -2LAC BLAZARS TO DIFFUSE TEV–PEV NEUTRINO FLUX

Abstract

The recent discovery of a diffuse cosmic neutrino flux extending up to PeV energies raises the question of which astrophysical sources generate this signal. Blazars are one class of extragalactic sources which may produce such high-energy neutrinos. We present a likelihood analysis searching for cumulative neutrino emission from blazars in the 2nd Fermi -LAT AGN catalog (2LAC) using IceCube neutrino data set 2009-12, which was optimized for the detection of individual sources. In contrast to those in previous searches with IceCube, the populations investigated contain up to hundreds of sources, the largest one being the entire blazar sample in the 2LAC catalog. No significant excess is observed, and upper limits for the cumulative flux from these populations are obtained. These constrain the maximum contribution of 2LAC blazars to the observed astrophysical neutrino flux to 27% or less between around 10 TeV and 2 PeV, assuming the equipartition of flavors on Earth and a single power-law spectrum with a spectral index of −2.5. We can still exclude the fact that 2LAC blazars (and their subpopulations) emit more than 50% of the observed neutrinos up to a spectral index as hard as −2.2 in the same energy range. Our result takes intomore » account the fact that the neutrino source count distribution is unknown, and it does not assume strict proportionality of the neutrino flux to the measured 2LAC γ -ray signal for each source. Additionally, we constrain recent models for neutrino emission by blazars.« less

Authors:
 [1];  [2];  [3];  [4]; ;  [5];  [6];  [7]; ;  [8];  [9]; ;  [10]; ;  [11]; ;  [12];  [13];  [14];  [15] more »; ; « less
  1. Department of Physics, University of Adelaide, Adelaide, 5005 (Australia)
  2. Physik-department, Technische Universität München, D-85748 Garching (Germany)
  3. DESY, D-15735 Zeuthen (Germany)
  4. Dept. of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch (New Zealand)
  5. Université Libre de Bruxelles, Science Faculty CP230, B-1050 Brussels (Belgium)
  6. Dept. of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin, Madison, WI 53706 (United States)
  7. Oskar Klein Centre and Dept. of Physics, Stockholm University, SE-10691 Stockholm (Sweden)
  8. Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen (Germany)
  9. Department of Physics, Marquette University, Milwaukee, WI, 53201 (United States)
  10. Dept. of Physics, Pennsylvania State University, University Park, PA 16802 (United States)
  11. Institute of Physics, University of Mainz, Staudinger Weg 7, D-55099 Mainz (Germany)
  12. Dept. of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
  13. III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen (Germany)
  14. Physics Department, South Dakota School of Mines and Technology, Rapid City, SD 57701 (United States)
  15. Dept. of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
Publication Date:
OSTI Identifier:
22664011
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; BL LACERTAE OBJECTS; CATALOGS; COSMIC NEUTRINOS; DATA ANALYSIS; DETECTION; EMISSION; FLAVOR MODEL; GALAXIES; GAMMA RADIATION; ICECUBE NEUTRINO DETECTOR; PEV RANGE; QUASARS; SPECTRA; TEV RANGE

Citation Formats

Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ansseau, I., Ahlers, M., Ahrens, M., Altmann, D., Anton, G., Andeen, K., Anderson, T., Arlen, T. C., Archinger, M., Baum, V., Arguelles, C., Axani, S., Auffenberg, J., Bai, X., Barwick, S. W., E-mail: thorsten.gluesenkamp@fau.de, Collaboration: IceCube Collaboration, and and others. THE CONTRIBUTION OF FERMI -2LAC BLAZARS TO DIFFUSE TEV–PEV NEUTRINO FLUX. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/1/45.
Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ansseau, I., Ahlers, M., Ahrens, M., Altmann, D., Anton, G., Andeen, K., Anderson, T., Arlen, T. C., Archinger, M., Baum, V., Arguelles, C., Axani, S., Auffenberg, J., Bai, X., Barwick, S. W., E-mail: thorsten.gluesenkamp@fau.de, Collaboration: IceCube Collaboration, & and others. THE CONTRIBUTION OF FERMI -2LAC BLAZARS TO DIFFUSE TEV–PEV NEUTRINO FLUX. United States. doi:10.3847/1538-4357/835/1/45.
Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ansseau, I., Ahlers, M., Ahrens, M., Altmann, D., Anton, G., Andeen, K., Anderson, T., Arlen, T. C., Archinger, M., Baum, V., Arguelles, C., Axani, S., Auffenberg, J., Bai, X., Barwick, S. W., E-mail: thorsten.gluesenkamp@fau.de, Collaboration: IceCube Collaboration, and and others. Fri . "THE CONTRIBUTION OF FERMI -2LAC BLAZARS TO DIFFUSE TEV–PEV NEUTRINO FLUX". United States. doi:10.3847/1538-4357/835/1/45.
@article{osti_22664011,
title = {THE CONTRIBUTION OF FERMI -2LAC BLAZARS TO DIFFUSE TEV–PEV NEUTRINO FLUX},
author = {Aartsen, M. G. and Abraham, K. and Ackermann, M. and Adams, J. and Aguilar, J. A. and Ansseau, I. and Ahlers, M. and Ahrens, M. and Altmann, D. and Anton, G. and Andeen, K. and Anderson, T. and Arlen, T. C. and Archinger, M. and Baum, V. and Arguelles, C. and Axani, S. and Auffenberg, J. and Bai, X. and Barwick, S. W., E-mail: thorsten.gluesenkamp@fau.de and Collaboration: IceCube Collaboration and and others},
abstractNote = {The recent discovery of a diffuse cosmic neutrino flux extending up to PeV energies raises the question of which astrophysical sources generate this signal. Blazars are one class of extragalactic sources which may produce such high-energy neutrinos. We present a likelihood analysis searching for cumulative neutrino emission from blazars in the 2nd Fermi -LAT AGN catalog (2LAC) using IceCube neutrino data set 2009-12, which was optimized for the detection of individual sources. In contrast to those in previous searches with IceCube, the populations investigated contain up to hundreds of sources, the largest one being the entire blazar sample in the 2LAC catalog. No significant excess is observed, and upper limits for the cumulative flux from these populations are obtained. These constrain the maximum contribution of 2LAC blazars to the observed astrophysical neutrino flux to 27% or less between around 10 TeV and 2 PeV, assuming the equipartition of flavors on Earth and a single power-law spectrum with a spectral index of −2.5. We can still exclude the fact that 2LAC blazars (and their subpopulations) emit more than 50% of the observed neutrinos up to a spectral index as hard as −2.2 in the same energy range. Our result takes into account the fact that the neutrino source count distribution is unknown, and it does not assume strict proportionality of the neutrino flux to the measured 2LAC γ -ray signal for each source. Additionally, we constrain recent models for neutrino emission by blazars.},
doi = {10.3847/1538-4357/835/1/45},
journal = {Astrophysical Journal},
number = 1,
volume = 835,
place = {United States},
year = {Fri Jan 20 00:00:00 EST 2017},
month = {Fri Jan 20 00:00:00 EST 2017}
}
  • We present a determination of the distributions of gamma-ray flux - the so called LogN-LogS relation - and photon spectral index for the 352 blazars detected with a greater than approximately seven sigma detection threshold and located above {+-} 20{sup o} Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true LogN-LogS counts or the true distribution of the photon index. We use the non-parametric methods developed by Efron and Petrosian to reconstructmore » the intrinsic distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation among the two variables. We demonstrate the robustness of our procedures using a simulated data set of blazars and then apply these to the real data and find that for the population as a whole the intrinsic flux distribution can be represented by a broken power law of slopes -2.37 {+-} 0.13 and -1.70 {+-} 0.26, and the intrinsic photon index distribution can be represented by a Gaussian with mean 2.41 {+-} 0.13 and 1{sigma} width of 0.25 {+-} 0.03. We also find the intrinsic distributions for the sub-populations of BL Lac and FSRQs type blazars separately. We then calculate the contribution of blazars to the diffuse cosmic gamma-ray background radiation to be 28% {+-} 19%.« less
  • We present a determination of the distributions of the photon spectral index and gamma-ray flux-the so-called log N-log S relation-for the 352 blazars detected with a greater than approximately 7{sigma} detection threshold and located above {+-}20 Degree-Sign Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true log N-log S counts or the true distribution of the photon index. We use the non-parametric methods developed by Efron and Petrosian to reconstruct the intrinsicmore » distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation between the two variables. We demonstrate the robustness of our procedures using a simulated data set of blazars and then apply these to the real data and find that for the population as a whole the intrinsic flux distribution can be represented by a broken power law with high and low indices of -2.37 {+-} 0.13 and -1.70 {+-} 0.26, respectively, and the intrinsic photon index distribution can be represented by a Gaussian with mean of 2.41 {+-} 0.13 and width of 0.25 {+-} 0.03. We also find the intrinsic distributions for the sub-populations of BL Lac and flat spectrum radio quasar type blazars separately. We then calculate the contribution of Fermi blazars to the diffuse extragalactic gamma-ray background radiation. Under the assumption that the flux distribution of blazars continues to arbitrarily low fluxes, we calculate the best-fit contribution of all blazars to the total extragalactic gamma-ray output to be 60%, with a large uncertainty.« less
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