In cosmic ray physics extensive progress has been made in recent years, both concerning theory and observation. The vast details in direct, indirect and secondary detections on the one hand provide ...the basis for a detailed modeling of the signatures via cosmic-ray transport and interaction, paving the way for the identification of Galactic cosmic-ray sources. On the other hand, the large number of constraints from different channels of cosmic-ray observables challenges these models frequently.
In this review, we will summarize the state-of-the art of the detection of cosmic rays and their secondaries, followed by a discussion what we can learn from coupling our knowledge of the cosmic-ray observables to the theory of cosmic-ray transport in the Galactic magnetic field. Finally, information from neutral secondaries will be added to draw a multimessenger-picture of the non-thermal sky, in which the hypothesis of supernova remnants as the dominant sources survives best. While this has been known since the 1930s, evidence for this scenario is steadily growing, with the first possible detection of hadronic signatures at GeV energies detected for three SNRs with Fermi. The existence of SNRs as PeVatrons, however, is not validated yet. The discussion of this and other open questions concerning the level of anisotropy, composition and spectral shape of the cosmic-ray energy spectrum is reviewed. Future perspectives of how to find the smoking cosmic-ray source gun concludes this review.
Abstract
The origin of astrophysical high-energy neutrinos detected by the IceCube Neutrino Observatory remains a mystery to be solved. In this paper we search for neutrino source candidates within ...the 90% containment area of 70 track-type neutrino events recorded by the IceCube Neutrino Observatory. By employing the Fermi-LAT 4FGL-DR2, the Swift-XRT 2SXPS, and the CRATES catalogs, we identify possible gamma-ray, X-ray, and flat-spectrum radio candidate sources of track-type neutrinos. We find that based on the brightness of sources and their spatial correlation with the track-type IceCube neutrinos, the constructed neutrino samples represent special populations of sources taken from the full Fermi-LAT 4FGL-DR2/Swift-XRT 2SXPS/CRATES catalogs with similar significance (2.1
σ
, 1.2
σ
, 2
σ
at 4.8 GHz, 2.1
σ
at 8.4 GHz, respectively, assuming 50% astrophysical signalness). After collecting redshifts and deriving subsamples of the CRATES catalog complete in the redshift–luminosity plane, we find that the 4.8 GHz (8.4 GHz) subsample can explain between 4% and 53% (3% and 42%) of the neutrinos (90% C.L.), when the probability of detecting a neutrino is proportional to the (
k
-corrected) radio flux. The overfluctuations indicate that a part of the sample is likely to contribute and that more sophisticated schemes in the source catalog selection are necessary to identify the neutrino sources at the 5
σ
level. Our selection serves as a starting point to further select the correct sources.
Context.
Indirect observations of the cosmic-ray electron (CRE) distribution via synchrotron emission is crucial for deepening the understanding of the CRE transport in the interstellar medium, and ...in investigating the role of galactic outflows.
Aims.
In this paper, we quantify the contribution of diffusion- and advection-dominated transport of CREs in the galaxy M51 considering relevant energy loss processes.
Methods.
We used recent measurement from M 51 that allow for the derivation of the diffusion coefficient, the star formation rate, and the magnetic field strength. With this input, we solved the 3D transport equation numerically including the spatial dependence as provided by the measurements, using the open-source transport framework CRPropa (v3.1). We included 3D transport (diffusion and advection), and the relevant loss processes.
Results.
We find that the data can be described well with the parameters from recent measurements. For the best fit, it is required that the wind velocity, following from the observed star formation rate, must be decreased by a factor of 5. We find a model in which the inner galaxy is dominated by advective escape and the outer galaxy is composed by both diffusion and advection.
Conclusions.
Three-dimensional modelling of cosmic-ray transport in the face-on galaxy M51 allows for conclusions about the strength of the outflow of such galaxies by quantifying the need for a wind in the description of the cosmic-ray signatures. This opens up the possibility of investigating galactic winds in face-on galaxies in general.
ABSTRACT
The recent detections of binary stellar mass black hole mergers by the LIGO and Virgo Collaborations suggest that such mergers are common occurrences. Galaxy mergers further indicate that ...supermassive black holes in centres of galaxies also merge and are typically expected to have had at least one merger in their lifetime, possibly many. In the presence of a jet, these mergers are almost always accompanied by a change of the jet direction and a connected jet precession motion, leading to interactions of the jet with ambient matter and producing high-energy particles, and consequently high-energy gamma-rays and neutrinos. In this work, we investigate the possibility under which conditions such mergers could be the sources of the diffuse astrophysical neutrino flux measured by the IceCube Neutrino Observatory. The main free parameters in the calculation concern the frequency of the mergers and the fraction of energy that is transferred from the gravitationally released energy to neutrinos. We show that the merger rate for SMBBHs must lie between ∼10−7 and 10−5 Gpc−3 yr−1. The ratio of energy going to neutrinos during such mergers lies then between ∼10−6 and 3 × 10−4. For stellar mass BBH mergers, the rate needs to be ∼10–100 Gpc−3 yr−1 and the expected ratio of neutrino to GW energy lies in a comparable range as for SMBBHs, ∼2 × 10−5–10−3. These values lie in a reasonable parameter range, so that the production of neutrinos at the level of the detected neutrino flux is a realistic possibility.
In this paper, we present high-energy neutrino spectra from 21 Galactic supernova remnants (SNRs), derived from gamma-ray measurements in the GeV–TeV range. We find that only the strongest sources, ...i.e. G40.5-0.5 in the north and Vela Junior in the south could be detected as single point sources by IceCube or KM3NeT, respectively. For the first time, it is also possible to derive a diffuse signal by applying the observed correlation between gamma-ray emission and radio signal. Radio data from 234 supernova remnants listed in Green’s catalog are used to show that the total diffuse neutrino flux is approximately a factor of 2.5 higher compared to the sources that are resolved so far. We show that the signal at above 10TeV energies can actually become comparable to the diffuse neutrino flux component from interactions in the interstellar medium. Recently, the IceCube collaboration announced the detection of a first diffuse signal of astrophysical high-energy neutrinos. Directional information cannot unambiguously reveal the nature of the sources at this point due to low statistics. A number of events come from close to the Galactic center and one of the main questions is whether at least a part of the signal can be of Galactic nature. In this paper, we show that the diffuse flux from well-resolved SNRs is at least a factor of 20 below the observed flux.
ABSTRACT
With the coincident detection of a gamma-ray flare and a neutrino from the blazar TXS 0506+056, active galactic nuclei (AGNs) have been put into focus as possible sources of the diffuse ...neutrino flux. We present a space and time-resolved model of the high-energy particle emission of a plasmoid assumed to travel along the axis of an AGN jet at relativistic speed. This was achieved by modifying the publicly available crpropa (version 3.1+) propagation framework that in our work is capable of being applied to source physics on sub-kpc scales. The propagation of a population of primary protons is modelled in a purely turbulent magnetic field and we take into account interactions of these protons with photons scattered from the accretion disc, synchrotron radiation emitted by ambient relativistic electrons, as well with themselves and with other ambient matter. Our model produces a PeV-neutrino flare caused mainly by photohadronic interactions of primaries with the accretion disc field. Secondary high-energy gamma-rays partly attenuate with the ambient photon fields whose combined optical depths achieve their minimal opacity for photons of around 10 TeV. Thus, our model is well capable of producing neutrino flares with a significantly reduced emission of gamma-rays in jets with a hadronic jet component that in the future can be fit to specific AGN flare scenarios.
Galactic cosmic rays (GCRs) and (anisotropically injected) extragalactic cosmic rays (EGCRs) are both affected by the Galactic magentic field (GMF) on their voyage to Earth at energies pertaining to ...the transition from GCRs to EGCRs, such that their flux, composition and arrival directions are modified. GCRs increasingly leak from the Galaxy with rising energy, leading to a flux suppression. The flux modification imposed on EGCRs is more complex, but may exhibit (subtle) spectral breaks depending on the direction and nature of the injected anisotropy.
Using a full Monte Carlo approach with CRPropa and making realistic and minimal assumptions about the injected GCR and EGCR fluxes, we derive a prediction of the total all-particle flux in the transition region. We find that it cannot account for the flux measured by various cosmic ray experiments in this energy range. This calls for the need of an additional component to the flux in the transition region.
Abstract
We draw a multimessenger picture of J1048+7143, a flat-spectrum radio quasar known to show quasiperiodic oscillations in the
γ
-ray regime. We generate the adaptively binned Fermi Large Area ...Telescope light curve of this source above 168 MeV to find three major
γ
-ray flares of the source, such that each of the three flares consists of two sharp subflares. Based on radio interferometric imaging data taken with the Very Large Array, we find that the kiloparsec-scale jet is directed west, while our analysis of 8.6 GHz very long baseline interferometry data, mostly taken with the Very Long Baseline Array, revealed signatures of two parsec-scale jets, one pointing east, one pointing south. We suggest that the misalignment of the kiloparsec- and parsec-scale jets is a revealing signature of jet precession. We also analyze the 5 GHz total flux density curve of J1048+7143 taken with the Nanshan (Ur) and RATAN-600 single-dish radio telescopes and find two complete radio flares, lagging slightly behind the
γ
-ray flares. We model the timing of
γ
-ray flares as a signature of the spin–orbit precession in a supermassive black hole binary, and find that the binary could merge in the next ∼60–80 yr. We show that both pulsar timing arrays and the planned Laser Interferometer Space Antenna lack sensitivity and frequency coverage to detect the hypothetical supermassive black hole binary in J1048+7143. We argue that the identification of sources similar to J1048+7143 plays a key role in revealing periodic high-energy sources in the distant universe.
Charmed Galaxies Becker Tjus, Julia; Rhode, Wolfgang
EPJ Web of Conferences,
2023, Volume:
290
Journal Article, Conference Proceeding
Peer reviewed
Open access
The quest for finding the origins of cosmic rays has been going on for many decades. Cosmic rays as charged particles react to cosmic magnetic fields and typically travel in diffusive motion through ...the Universe. Their imprint on Earth therefore holds little information on their origin, and finding the sources of cosmic rays is a major challenge. The question of their origins has been a leading questions in physics and astrophysics in the past decades. To solve this riddle, a multimessenger approach is used, including cosmic-ray interaction products in the searches, specifically gamma-rays and neutrinos produced in the resulting particle showers. In this multimessenger picture, the detection of high-energy neutrinos from the cosmos by IceCube - as a unique tracer of cosmic rays - is an important piece of the puzzle. First evidence for neutrino emission from the active galaxies TXS0506+056 and NGC1068 indicates that a significant fraction comes from such sources. In this paper, the intriguing fact that gamma-rays seem to be absorbed in these sources discussed. The possibility of neutrinos being produced in regions of high photon or gas densities, together with the possibility of in the future revealing neutrinos from the decay of charmed particles, will be investigated, possibly opening a window to
Charmed Galaxies
.
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