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11.
Evidence for a supergalactic structure of magnetic deflection multiplets of ultra-high-energy cosmic rays
R. U. Abbasi, T. Abu-Zayyad, Mitsuhiro Abe, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, D. R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, izvirni znanstveni članek

Opis: Evidence for a large-scale supergalactic cosmic-ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high-energy cosmic-ray (UHECR) energies above 1019 eV using 7 years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy–position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, because the supergalactic plane is a fit to the average matter density of the local large-scale structure, UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire field-of-view (FOV) behavior of the strength of intermediate-scale energy–angle correlations. These multiplets are measured in spherical cap section bins (wedges) of the FOV to account for coherent and random magnetic fields. The structure found is consistent with supergalactic deflection, the previously published energy spectrum anisotropy results of the TA (the Hotspot and Coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data posttrial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.2σ. The 10 years of data posttrial significance is 4.1σ. Furthermore, the starburst galaxy M82 is shown to be a possible source of the TA Hotspot, and an estimate of the supergalactic magnetic field using UHECR measurements is presented.
Najdeno v: ključnih besedah
Povzetek najdenega: ...ultra-high-energy cosmic radiation, cosmic rays, high energy astrophysics, astrophysical magnetism, cosmic ray astronomy, cosmic ray...
Ključne besede: extragalactic magnetic fields, ultra-high-energy cosmic radiation, cosmic rays, high energy astrophysics, astrophysical magnetism, cosmic ray astronomy, cosmic ray sources
Objavljeno: 05.02.2021; Ogledov: 1276; Prenosov: 90
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Study of axion-like particles signatures in the very-high-energy gamma-ray spectra of Active Galactic Nuclei
Ivana Batković, 2020, magistrsko delo

Najdeno v: ključnih besedah
Ključne besede: axions, dark matter, gamma-ray astrophysics
Objavljeno: 26.02.2021; Ogledov: 1395; Prenosov: 0
.pdf Polno besedilo (12,57 MB)

14.
Studying dark matter annihilation in Perseus galaxy cluster using very-high-energy gamma rays
Nemanja Ivković, 2020, magistrsko delo

Najdeno v: ključnih besedah
Ključne besede: dark matter, gamma-ray astrophysics
Objavljeno: 01.03.2021; Ogledov: 1252; Prenosov: 0
.pdf Polno besedilo (7,17 MB)

15.
Space-time ripples
Taj Jankovič, 2017, strokovni članek

Opis: Recent first direct detection of gravitational waves opened a new window on the universe. Gravitational waves arise from small perturbations of space-time and from their characteristics it is possible to determine properties of astrophysical objects from which they originate. In this seminar Einstein equation is introduced to describe gravitational waves and ascertain their properties. Furthermore, possible astrophysical sources are presented, as well as the first directly and indirectly detected event.
Najdeno v: ključnih besedah
Ključne besede: gravitation, gravitational waves, theory of relativity, astrophysics
Objavljeno: 29.07.2021; Ogledov: 814; Prenosov: 0

16.
Two-integral distribution functions in axisymmetric galaxies: Implications for dark matter searches
Piero Ullio, Mihael Petač, 2019, izvirni znanstveni članek

Opis: We address the problem of reconstructing the phase-space distribution function for an extended collisionless system, with known density profile and in equilibrium within an axisymmetric gravitational potential. Assuming that it depends on only two integrals of motion, namely the energy and the component of the angular momentum along the axis of symmetry Lz , there is a one-to-one correspondence between the density profile and the component of the distribution function that is even in Lz, as well as between the weighted azimuthal velocity profile and the odd component. This inversion procedure was originally proposed by Lynden-Bell and later refined in its numerical implementation by Hunter and Qian; after overcoming a technical difficulty, we apply it here for the first time in presence of a strongly flattened component, as a novel approach of extracting the phase-space distribution function for dark matter particles in the halo of spiral galaxies. We compare results obtained for realistic axisymmetric models to those in the spherical symmetric limit as assumed in previous analyses, showing the rather severe shortcomings in the latter. We then apply the scheme to the Milky Way and discuss the implications for the direct dark matter searches. In particular, we reinterpret the null results of the Xenon1T experiment for spin-(in)dependent interactions and make predictions for the annual modulation of the signal for a set of axisymmetric models, including a self-consistently defined corotating halo.
Najdeno v: ključnih besedah
Povzetek najdenega: ...dark matter, astrophysics of galaxies, high energy physics, phenomenology...
Ključne besede: dark matter, astrophysics of galaxies, high energy physics, phenomenology
Objavljeno: 01.10.2021; Ogledov: 727; Prenosov: 0
.pdf Polno besedilo (1,22 MB)

17.
Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulations
Emmanuel Nezri, Julien Lavalle, Arturo Núñez-Castiñeyra, Mihael Petač, 2021, izvirni znanstveni članek

Opis: Signal predictions for galactic dark matter (DM) searches often rely on assumptions regarding the DM phase-space distribution function (DF) in halos. This applies to both particle (e.g. p-wave suppressed or Sommerfeld-enhanced annihilation, scattering off atoms, etc.) and macroscopic DM candidates (e.g. microlensing of primordial black holes). As experiments and observations improve in precision, better assessing theoretical uncertainties becomes pressing in the prospect of deriving reliable constraints on DM candidates or trustworthy hints for detection. Most reliable predictions of DFs in halos are based on solving the steady-state collisionless Boltzmann equation (e.g. Eddington-like inversions, action-angle methods, etc.) consistently with observational constraints. One can do so starting from maximal symmetries and a minimal set of degrees of freedom, and then increasing complexity. Key issues are then whether adding complexity, which is computationally costy, improves predictions, and if so where to stop. Clues can be obtained by making predictions for zoomed-in hydrodynamical cosmological simulations in which one can access the true (coarse-grained) phase-space information. Here, we test an axisymmetric extension of the Eddington inversion to predict the full DM DF from its density profile and the total gravitational potential of the system. This permits to go beyond spherical symmetry, and is a priori well suited for spiral galaxies. We show that axisymmetry does not necessarily improve over spherical symmetry because the (observationally unconstrained) angular momentum of the DM halo is not generically aligned with the baryonic one. Theoretical errors are similar to those of the Eddington inversion though, at the 10-20% level for velocity-dependent predictions related to particle DM searches in spiral galaxies. We extensively describe the approach and comment on the results.
Najdeno v: ključnih besedah
Povzetek najdenega: ...matter simulations, dark matter theory, cosmology, nongalactic astrophysics, astrophysics of galaxies, high energy physics...
Ključne besede: galaxy dynamics, dark matter experiments, dark matter simulations, dark matter theory, cosmology, nongalactic astrophysics, astrophysics of galaxies, high energy physics
Objavljeno: 01.10.2021; Ogledov: 743; Prenosov: 31
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18.
Equilibrium axisymmetric halo model for the Milky Way and its implications for direct and indirect dark matter searches
Mihael Petač, 2020, izvirni znanstveni članek

Opis: We for the first time provide self-consistent axisymmetric phase-space distribution models for the Milky Way's dark matter (DM) halo which are carefully matched against the latest kinematic measurements through Bayesian analysis. By using broad priors on the individual galactic components, we derive conservative estimates for the astrophysical factors entering the interpretation of direct and indirect DM searches. While the resulting DM density profiles are in good agreement with previous studies, implying ρ⊙≈10-2 M⊙/pc3, the presence of baryonic disc leads to significant differences in the local DM velocity distribution in comparison with the standard halo model. For direct detection, this implies roughly 30% stronger cross section limits at DM masses near detectors maximum sensitivity and up to an order of magnitude weaker limits at the lower end of the mass range. Furthermore, by performing Monte Carlo simulations for the upcoming DARWIN and DarkSide-20k experiments, we demonstrate that upon successful detection of heavy DM with coupling just below the current limits, the carefully constructed axisymmetric models can eliminate bias and reduce uncertainties by more then 50% in the reconstructed DM coupling and mass, but also help in a more reliable determination of the scattering operator. Furthermore, the velocity anisotropies induced by the baryonic disc can lead to significantly larger annual modulation amplitude and sizable differences in the directional distribution of the expected DM-induced events. For indirect searches, we provide the differential J factors and compute several moments of the relative velocity distribution that are needed for predicting the rate of velocity-dependent annihilations. However, we find that accurate predictions are still hindered by large uncertainties regarding the DM distribution near the galactic center.
Najdeno v: ključnih besedah
Povzetek najdenega: ...dark matter, astrophysics, galaxies, high energy physics, experiments, phenomenology...
Ključne besede: dark matter, astrophysics, galaxies, high energy physics, experiments, phenomenology
Objavljeno: 01.10.2021; Ogledov: 683; Prenosov: 20
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19.
Synergies of THESEUS with the large facilities of the 2030s and guest observer opportunities
P. Rosati, S. Basa, A. W. Blain, E. Bozzo, Marica Branchesi, L. Christensen, A. Ferrara, Andreja Gomboc, P. T. O'Brien, J. P. Osborne, 2021, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...multi-messenger astrophysics, Gamma-ray bursts, X-ray sources, gravitation wave sources...
Ključne besede: multi-messenger astrophysics, Gamma-ray bursts, X-ray sources, gravitation wave sources
Objavljeno: 02.11.2021; Ogledov: 566; Prenosov: 0
.pdf Polno besedilo (2,75 MB)

20.
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