IceCube Science Halzen, Francis
Journal of physics. Conference series,
06/2009, Volume:
171, Issue:
1
Journal Article
Peer reviewed
Open access
We discuss the status of the kilometer-scale neutrino detector IceCube and its low energy upgrade Deep Core and review its scientific potential for particle physics. We subsequently appraise ...IceCube's potential for revealing the enigmatic sources of cosmic rays. After all, this aspiration set the scale of the instrument. While only a smoking gun is missing for the case that the Galactic component of the cosmic ray spectrum originates in supernova remnants, the origin of the extragalactic component remains as inscrutable as ever. We speculate on the role of the nearby active galaxies Centaurus A and M87.
Issue Title: The Multi-Messenger Approach to High-Energy Gamma-Ray Sources: Third Workshop on the Nature of Unidentified High-Energy Sources Although kilometer-scale neutrino detectors such as ...IceCube are discovery instruments, their conceptual design is very much anchored to the observational fact that Nature produces protons and photons with energies in excess of 10^sup 20^ eV and 10^sup 13^ eV, respectively. The puzzle of where and how Nature accelerates the highest energy cosmic particles is unresolved almost a century after their discovery. From energetics considerations we anticipate on the order of 10-100 neutrino events per kilometer squared per year pointing back at the source(s) of both galactic and extragalactic cosmic rays. In this context, we discuss the results of the AMANDA and IceCube neutrino telescopes which will deliver a kilometer-square-year of data over the next 3 years. PUBLICATION ABSTRACT
Active galactic nuclei (AGN) are believed to be the source of ultra high energy cosmic rays (UHECRs, E>1018eV). Particles are assumed to be accelerated in the accretion disk and the plasma jets, ...produced due to conservation of angular momentum, to the highest energies, where they interact with each other and produce pions, which decay among others in neutrinos.
For a known cosmic ray (CR) spectral behavior, the main parameters in the calculation of the neutrino flux from proton–proton (p–p) interactions are the target density nH and the ratio of electrons to protons fe. Using most recent neutrino flux limits from IceCube point source searches, we set limits on the target densities for 33 FR-I galaxies. The densities are shown to be smaller than 30cm-3 to 2·103cm-3, depending on the source and when using a fixed electron to proton ratio of fe=0.1. This implies that some CR acceleration sites, especially those close to the core of the AGN, can already be excluded, or else that the ratio of electrons to protons deviates significantly from the commonly used value of 0.1.
For Centaurus A (Cen A) and Messier 87 (M 87) we use Fermi observations to model the γ-flux, the neutrino flux and the resulting target density. The detection of these neutrinos will help to find information about acceleration processes in the source.
New angle on cosmic rays Gallagher, John S.; Halzen, Francis
Science (American Association for the Advancement of Science),
09/2017, Volume:
357, Issue:
6357
Journal Article
Peer reviewed
A substantial directional anisotropy is observed for ultrahigh-energy cosmic rays
Cosmic rays are nuclei that have been accelerated to relativistic velocities by astrophysical sources, arriving at ...Earth after traversing the space between us and the source. As electrically charged particles, they are deflected by magnetic fields, which scramble their directions in space (
1
). Finding deviations from the highly isotropic angular distribution of high-energy cosmic rays in the sky has long been a prime goal of cosmic-ray researchers. Marginal detections have been reported in the past that failed to hold up. On page 1266 of this issue, The Pierre Auger Collaboration (
2
) report a strong detection of a pronounced anisotropy in the arrival directions of cosmic rays with energies (
E
) of ≥8 EeV (8 × 10
18
electron volts), indicating that they are of extragalactic origin.
Neutrino Astronomy: An Update Halzen, Francis
Proceedings of the International Astronomical Union,
08/2012, Volume:
8, Issue:
S288
Journal Article
Peer reviewed
Open access
Detecting neutrinos associated with the still enigmatic sources of cosmic rays has reached a new watershed with the completion of IceCube, the first detector with sensitivity to the anticipated ...fluxes. In this review, we will briefly revisit the rationale for constructing kilometer-scale neutrino detectors and summarize the status of the field.
The IceCube project transformed a cubic kilometer of transparent, natural Antarctic ice into a Cherenkov detector. It discovered neutrinos of TeV-PeV energy originating beyond our Galaxy with an ...energy flux that exceeds the one of high-energy gamma rays of extragalactic origin. Unlike at any other wavelength of light, extragalactic neutrinos outshine the nearby sources in our own Milky way. Updated measurements of the diffuse cosmic neutrino flux indicate that the high-energy gamma rays produced by the neutral pions that accompany cosmic neutrinos lose energy in the sources and are likely to be observed at MeV energy, or below. After the reanalysis of 10 years of archival data with an improved data selection and enhanced data analysis methods, the active galaxy NGC 1068 emerged as the hottest spot in the neutrino sky map. It is also the most significant source in a search at the positions of 110 preselected high-energy gamma-ray sources. Additionally, we find evidence for neutrino emission from the active galaxies PKS 1424+240 and TXS 0506+056. TXS 0506+056 had already been identified as a neutrino source in a multimessenger campaign triggered by a neutrino of 290 TeV energy and, by the independent observation of a neutrino burst in 2014 from this source in archival IceCube data. The observations point to active galaxies as the sources of cosmic neutrinos, and cosmic rays, with the gamma-ray-obscured dense cores near the supermassive black holes at their center as the sites where neutrinos originate, typically within \(10\sim100\) Schwarzschild radii.
We estimate the neutrino emission from individual γ-ray bursts observed by the BATSE detector on the Compton Gamma-Ray Observatory. Neutrinos are produced by photoproduction of pions when protons ...interact with photons in the region where the kinetic energy of the relativistic fireball is dissipated allowing the acceleration of electrons and protons. We also consider models where neutrinos are predominantly produced on the radiation surrounding the newly formed black hole. From the observed redshift and photon flux of each individual burst, we compute the neutrino flux in a variety of models based on the assumption that equal kinetic energy is dissipated into electrons and protons. Where not measured, the redshift is estimated by other methods. Unlike previous calculations of the universal diffuse neutrino flux produced by all γ-ray bursts, the individual fluxes (compiled at
http://www.arcetri.astro.it/~dafne/grb/) can be directly compared with coincident observations by the AMANDA telescope at the South Pole. Because of its large statistics, our predictions are likely to be representative for future observations with larger neutrino telescopes.
We perform a realistic evaluation of the potential of IceCube, a kilometer-scale neutrino detector under construction at the South Pole, to detect neutrinos in the direction of the potential ...accelerators of the Galactic cosmic rays. We take fully account of the fact that the measurement of the energy of the secondary muons at the detector can be used to further discriminate between the signal and the background of atmospheric neutrinos. A PeVatron is defined as the accelerator of cosmic rays with energies of several PeV, the knee in the spectrum; it has a hard energy spectrum and produces secondary photons of hundreds of GeV on the interstellar medium. Assuming that the Milagro sources are PeVatrons, an IceCube analysis combining the information from the different sources can reveal them as such at the 3
σ level in one year and at the 5
σ level in three years. We discuss the dependence of these expectations on the considerable ambiguities associated with the source spectra.
PDF
