ABSTRACT
The gamma-ray emission from Starburst and Star-forming Galaxies (SBGs and SFGs) strongly suggests a correlation between star-forming activity and gamma-ray luminosity. However, the very ...nature of cosmic ray (CR) transport and the degree of their confinement within SBG cores are still open questions
. We aim at probing the imprints left by CR transport on gamma-ray and neutrino observations of point-like SFGs and SBGs, looking into quantitative ways to discriminate among different transport models. We analyse the 10-yr Fermi-LAT spectral energy distributions of 13 nearby galaxies with two different CR transport models, taking into account the corresponding IR and UV observations. We also generate mock gamma-ray data to simulate the CTA performance in detecting these sources. In this way, we propose a test to discriminate between the two CR models, quantifying the statistical confidence at which one model can be preferred over the other. We point out that the current data already give a slight preference to CR models that are dominated by advection. Moreover, we show that CTA will allow us to firmly disfavour models dominated by diffusion over self-induced turbulence, compared to advection-dominated models, with Bayes factors, which can be as large as 107 for some of the SBGs. Finally, we estimate the diffuse gamma-ray and neutrino fluxes of SFGs and SBGs, showing that they can explain $25{{\,\rm per\ cent}}$ of the diffuse HESE data while remaining consistent with gamma-ray limits on non-blazar sources.
The discovery of ultra-high-energy neutrinos, with energies above 100 PeV, may soon be within reach of upcoming neutrino telescopes. We present a robust framework to compute the statistical ...significance of point-source discovery via the detection of neutrino multiplets. We apply it to the radio array component of IceCube-Gen2. To identify a source with
3\sigma
3
σ
significance, IceCube-Gen2 will need to detect a triplet, at best, and an octuplet, at worst, depending on whether the source is steady-state or transient, and on its position in the sky. The discovery, or absence, of sources significantly constrains the properties of the source population.
Abstract
Star-forming and starburst galaxies, which are well-known cosmic-ray reservoirs, are expected to emit gamma-rays and neutrinos predominantly via hadronic collisions. In this Letter, we ...analyze the 10 yr Fermi-LAT spectral energy distributions of 13 nearby galaxies by means of a physical model which accounts for high-energy proton transport in starburst nuclei and includes the contribution of primary and secondary electrons. In particular, we test the hypothesis that the observed gamma-ray fluxes are mostly due to star-forming activity, in agreement with the available star formation rates coming from IR and UV observations. Through this observation-based approach, we determine the most likely neutrino counterpart from star-forming and starburst galaxies and quantitatively assess the ability of current and upcoming neutrino telescopes to detect them as pointlike sources. Remarkably, we find that the cores of the Small Magellanic Cloud and the Circinus galaxy are potentially observable by KM3NeT/ARCA with 6 yr of observation. Moreover, most of the nearby galaxies are likely to be just a factor of a few below the KM3NeT and IceCube-Gen2 pointlike sensitivities. After investigating the prospects for detection of gamma-rays above TeV energies from these sources, we conclude that the joint observations of high-energy neutrinos and gamma-rays with upcoming telescopes will be an objective test for our emission model and may provide compelling evidence of star-forming activity as a tracer of neutrino production.
Flavor-dependent neutrino transport is described by a well-known kinetic equation for occupation-number matrices in flavor space. However, in the context of fast flavor conversion, we identify an ...unforeseen predicament: the pivotal self-induced exponential growth of small inhomogeneities strongly violates conservation of neutrino-neutrino refractive energy. We prove that it is traded with the huge reservoir of neutrino kinetic energy through gradients of neutrino flavor coherence (the off-diagonal piece of the flavor density matrix) and derive the missing gradient terms. The usual equations remain sufficient to describe flavor evolution, at the cost of renouncing energy conservation, which cannot play any role in explaining the numerically observed final state. Published by the American Physical Society 2024
The OPERA Collaboration (2011) 1 has reported evidence of superluminal νμ propagation between CERN and the LNGS. Cohen and Glashow (2011) 2 argued that such neutrinos should lose energy by producing ...photons and e+e− pairs, through Z0 mediated processes analogous to Cherenkov radiation. In terms of the parameter δ≡(vν2−vc2)/vc2, the OPERA result corresponds to δ≈5⋅10−5. For this value (note that (vν−vc)/vc≈δ2≈2.5⋅10−5) of δ, a very significant deformation of the neutrino energy spectrum and an abundant production of photons and e+e− pairs should be observed at LNGS. We present an analysis based on the 2010 and part of the 2011 data sets from the ICARUS experiment, located at Gran Sasso National Laboratory and using the same neutrino beam from CERN. We find that the rates and deposited energy distributions of neutrino events in ICARUS agree with the expectations for an unperturbed spectrum of the CERN neutrino beam, as also reported by OPERA. Our results therefore refute a superluminal interpretation of the OPERA result according to the Cohen and Glashow (2011) prediction 2 for a weak current analog to Cherenkov radiation. In a dedicated search, no superluminal Cherenkov-like e+e− pair or γ emission event has been directly observed inside the fiducial volume of the “bubble chamber-like” ICARUS TPC-LAr detector, setting the much stricter limit of δ<2.5⋅10−8 at the 90% confidence level, comparable with the one due to the observations from the SN1987a (M.J. Longo, 1987 4). The observations of high energy neutrino events by Super-Kamiokande and IceCube are also pointing to a much stricter limit on δ.
Liquid Argon Time Projection Chamber (LAr TPC) detectors offer charged particle imaging capability with remarkable spatial resolution. Precise event reconstruction procedures are critical in order to ...fully exploit the potential of this technology. In this paper we present a new, general approach to 3D reconstruction for the LAr TPC with a practical application to the track reconstruction. The efficiency of the method is evaluated on a sample of simulated tracks. We present also the application of the method to the analysis of stopping particle tracks collected during the ICARUS T600 detector operation with the CNGS neutrino beam.
Abstract
The sources of IceCube neutrinos are as yet unknown. The multimessenger observation of their emission in
γ
-rays can be a guide to their identification, as exemplified by the case of TXS ...0506+056. We suggest a new method of searching for
γ
-rays with Imaging Air Cherenkov Telescopes from sources coinciding with possible astrophysical neutrinos. We propose that searches of
γ
-rays be extended from the current practice of only a few days to up to one month from a neutrino alert. We test this strategy on simulated sources modeled after the blazar TXS 0506+056, emitting neutrinos and
γ
-rays via photohadronic interactions: the
γ
-rays are subsequently reprocessed in the VHE range. Using MAGIC as a benchmark example, we show that current Cherenkov Telescopes should be able to detect
γ
-ray counterparts to neutrino alerts with a rate of approximately one per year. It has been proposed that the high-energy diffuse neutrino flux can be explained by ∼5% of all blazars flaring in neutrinos once every 10 yr, with a neutrino luminosity similar to that of TXS 0506+056 during the 2014–2015 neutrino flare. The implementation of our strategy could lead, over a timescale of one or a few years, either to the detection of this subclass of blazars contributing to the diffuse neutrino flux or to a constraint on this model.
PDF
