Context. The mass function of supermassive black holes in our cosmic neighborhood is required to understand the statistics of their activity and consequently the origin of ultra high energy ...particles. Aims. We determine a mass function of supermassive black hole candidates from the entire sky except for the Galactic plane. Methods. Using the 2MASS catalogue as a starting point, and the well-established correlation between black hole mass and the bulge of old population of stars, we derive a list of nearby black hole candidates within the redshift range z < 0.025, then perform an additional selection based on the Hubble type. We present our resulting catalogue elsewhere. The final list of black hole candidates above a mass of MBH > 3 × 106 $M_{\odot}$ has 5829 entries. We perform a Hubble-type correction to account for selection effects, which reduces this number to 2919 black hole candidates. Here we use this catalogue to derive the black-hole mass function. We also correct for volume, so that this mass function is a volume-limited distribution to redshift 0.025. Results. The differential mass function of nearby black hole candidates is a curved function, with a straight simple power-law of index -3 above 108 $M_{\odot}$ that becomes progressively flatter towards lower masses, turns off towards a gap below 3 × 106 $M_{\odot}$, and then extends into the range where nuclear star clusters replace black holes. The shape of this mass function can be explained in a simple merger picture. Integrating this mass function over the redshift range for which it has been derived, infers a total number of black holes with z < 0.025, and MBH > 107 $M_{\odot}$ of about 2.4 × 104, or, if we average uniformly, 0.6 for every square degree on the sky.
We update our previous search for trapped magnetic monopoles in LHC Run 2 using nearly six times more integrated luminosity and including additional models for the interpretation of the data. The ...MoEDAL forward trapping detector, comprising 222 kg of aluminium samples, was exposed to 2.11 fb−1 of 13 TeV proton–proton collisions near the LHCb interaction point and analysed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges equal to the Dirac charge or above are excluded in all samples. The results are interpreted in Drell–Yan production models for monopoles with spins 0, 1/2 and 1: in addition to standard point-like couplings, we also consider couplings with momentum-dependent form factors. The search provides the best current laboratory constraints for monopoles with magnetic charges ranging from two to five times the Dirac charge.
Supermassive black hole (BH) mergers with spin-flips accelerate energetic particles through their relativistic precessing jets, producing high-energy neutrinos and finally gravitational waves (GWs). ...In star formation, massive stars form in pairs, triplets, and quadruplets, allowing second-generation mergers of the remnants with discrepant spin directions. The GW data support such a scenario. Earlier, we suggested that stellar mass BH mergers (visible in M82) with an associated spin-flip analogously allow the acceleration of energetic particles, with ensuing high-energy neutrinos and high-energy photons, and finally produce GWs. At cosmic distances, only the GWs and the neutrinos remain detectable. In this study, we generalize the argument to starburst and normal galaxies throughout their cosmic evolution and show that these galaxies may dominate over active galactic nuclei (AGN) in the flux of ultra-high-energy particles observed at Earth. All these sources contribute to the cosmic neutrino background, as well as the GW background (they detected lower frequencies). We outline a search strategy to find such episodic sources, which requires including both luminosity and flux density.
The statistics of black holes and their masses strongly suggests that their mass distribution has a cut-off towards lower masses near 3 × 106 M⊙. This is consistent with a classical formation ...mechanism from the agglomeration of the first massive stars in the universe. However, when the masses of the stars approach 106 M⊙, the stars become unstable and collapse, possibly forming the first generation of cosmological black holes. Here, we speculate that the claimed detection of an isotropic radio background may constitute evidence of the formation of these first supermassive black holes, since their data are compatible in spectrum and intensity with synchrotron emission from the remnants. The model proposed fulfils all observational conditions for the background, in terms of single-source strength, number of sources, far-infrared and gamma-ray emission. The observed high-energy neutrino flux is consistent with our calculations in flux and spectrum. The proposal described in this paper may also explain the early formation and growth of massive bulge-less disc galaxies as derived from the massive, gaseous shell formed during the explosion prior to the formation of a supermassive black hole.
A model is introduced, in which the irregularity spectrum of the Galactic magnetic field beyond the dissipation length scale is first a Kolmogorov spectrum k-5/3 at small scales λ = 2 π/k with k the ...wave-number, then a saturation spectrum k-1, and finally a shock-dominated spectrum k-2 mostly in the halo/wind outside the Cosmic Ray disk. In an isotropic approximation such a model is consistent with the Interstellar Medium (ISM) data. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.
The Nature of Light Dark Matter Biermann, P L; Caramete, L; Munyaneza, F ...
Exotic Nuclei and Nuclear/Particle Astrophysics (II) (AIP Conference Proceedings Volume 972),
01/2008, Letnik:
972
Journal Article
Recenzirano
For over seventy years we have observed evidence for the presence of dark matter, now clearly shown to be non-baryonic. The microwave background fluctuations show that it is about 0.2 of all density ...of matter and energy, while baryonic matter is about 0.04; the rest is labelled dark energy, and not even close to an understanding. The sum is just what is required to make the universe geometrically flat. In this overview we discuss one of the attempts to explain the nature of dark matter, light dark matter, also called sterile neutrinos, or right-handed neutrinos, or more generally warm dark matter. Many of the predictions for cold dark matter and warm dark matter are the same, most of modifications are in small scales, in the temporal evolution of structure, and in some of the shapes of structure. We are now convinced that these warm dark matter particles have to be subthermal at injection to get the right free-streaming length in structure formation. Galaxies, their structure as well as their distribution pose a number of tests and riddles, not all of which have yet been passed or solved. We outline and summarize the latest evolution in these discussions, centering now on galaxies, their structure and evolution, as well as large scale distribution. Warm dark matter has survived many critical tests so far, and is clearly worth exploring in much more detail.
Gravitational wave astronomy has been already a well-established research domain for many years. Moreover, after the detection by LIGO/Virgo collaboration, in 2017, of the first gravitational wave ...signal emitted during the collision of a binary neutron star system, that was accompanied by the detection of other types of signals coming from the same event, multi-messenger astronomy has claimed its rights more assertively. In this context, it is of great importance in a gravitational wave experiment to have a rapid mechanism of alerting about potential gravitational waves events other observatories capable to detect other types of signals (e.g. in other wavelengths) that are produce by the same event. In this paper, we present the first progress in the development of a neural network algorithm trained to recognize and characterize gravitational wave patterns from signal plus noise data samples. We have implemented two versions of the algorithm, one that classifies the gravitational wave signals into 2 classes, and another one that classifies them into 4 classes, according to the mass ratio of the emitting source. We have obtained promising results, with 100% training and testing accuracy for the 2-class network and approximately 95% for the 4-class network. We conclude that the current version of the neural network algorithm demonstrates the ability of a well-configured and calibrated Bidirectional Long-Short Term Memory software to classify with very high accuracy and in an extremely short time gravitational wave signals, even when they are accompanied by noise. Moreover, the performance obtained with this algorithm qualifies it as a fast method of data analysis and can be used as a low-latency pipeline for gravitational wave observatories like the future LISA Mission.
Advanced
LIGO
detected a significant gravitational wave signal (GW170104) originating from the coalescence of two black holes during the second observation run on January 4th, 2017. An all-sky ...high-energy neutrino follow-up search has been made using data from the
Antares
neutrino telescope, including both upgoing and downgoing events in two separate analyses. No neutrino candidates were found within
±
500
s around the GW event time nor any time clustering of events over an extended time window of
±
3
months. The non-detection is used to constrain isotropic-equivalent high-energy neutrino emission from GW170104 to less than
∼
1.2
×
10
55
erg for a
E
-
2
spectrum. This constraint is valid in the energy range corresponding to the 5–95% quantiles of the neutrino flux 3.2 TeV; 3.6 PeV, if the GW emitter was below the
Antares
horizon at the alert time.
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