The Gamma-Ray Window to Intergalactic Magnetism

One of the most promising ways to probe intergalactic magnetic fields (IGMFs) is through gamma rays produced in electromagnetic cascades initiated by high-energy gamma rays or cosmic rays in the intergalactic space. Because the charged component of the cascade is sensitive to magnetic fields, gamma-ray observations of distant objects such as blazars can be used to constrain IGMF properties. Ground-based and space-borne gamma-ray telescopes deliver spectral, temporal, and angular information of high-energy gamma-ray sources, which carries imprints of the intervening magnetic fields. This provides insights into the nature of the processes that led to the creation of the first magnetic fields and into the phenomena that impacted their evolution. Here we provide a detailed description of how gamma-ray observations can be used to probe cosmic magnetism. We review the current status of this topic and discuss the prospects for measuring IGMFs with the next generation of gamma-ray observatories.

Axion-Like Particle Searches with IACTs

The growing interest in axion-like particles (ALPs) stems from the fact that they provide successful theoretical explanations of physics phenomena, from the anomaly of the CP-symmetry conservation in strong interactions to the observation of an unexpectedly large TeV photon flux from astrophysical sources, at distances where the strong absorption by the intergalactic medium should make the signal very dim. In this latter condition, which is the focus of this review, a possible explanation is that TeV photons convert to ALPs in the presence of strong and/or extended magnetic fields, such as those in the core of galaxy clusters or around compact objects, or even those in the intergalactic space. This mixing affects the observed γ-ray spectrum of distant sources, either by signal recovery or the production of irregularities in the spectrum, called `wiggles’, according to the specific microscopic realization of the ALP and the ambient magnetic field at the source, and in the Milky Way, where ALPs may be converted back to γ rays. ALPs are also proposed as candidate particles for the Dark Matter. Imaging Atmospheric Cherenkov telescopes (IACTs) have the potential to detect the imprint of ALPs in the TeV spectrum from several classes of sources. In this contribution, we present the ALP case and review the past decade of searches for ALPs with this class of instruments.

Einstein’s Misunderstanding of Time in the Time-Invariant Universe

Einstein has kept time as the dimension of the space-time continuum that is supposed to be a fundamental arena of the universe. Our research confirms time is the duration of changes, i.e., motion run in the time-invariant universal space that has Euclidean shape, it is infinite. Black holes in the center of galaxies are rejuvenating systems of the universe. In these black holes old matter is transforming back into the fresh energy of elementary that AGNs are throwing in the intergalactic space in the form of huge jests. These jets are fresh material for new star formation. The universal process of continuous rejuvenation is eternal.

Dust destruction at high galactic altitude

The possibility of destruction carbonaceous dust particles swept out by the radiation pressure into near-galactic space due to the relative motion of dust particles of various sizes is considered. The earlier model of the motion of dust in the Galaxy under the action of radiation pressure, gravity, and gas resistance is expanded taking into account the destruction processes. The possibility of dust sweeping is considered taking into account its collisions with the gas of the Galaxy and with other dust particles. Also, we clarify the range of particle sizes that can get into intergalactic space due to the described mechanism.

RETRACTED ARTICLE: Mass–Energy Equivalence Extension onto a Superfluid Quantum Vacuum

In contemporary physics, the model of space–time as the fundamental arena of the universe is replaced by some authors with the superfluid quantum vacuum. In a vacuum, time is not a fourth dimension of space, it is merely the duration of the physical changes, i.e. motion in a vacuum. Mass–energy equivalence has its origin in the variable density of the vacuum. Inertial mass and gravitational mass are equal and both originate in the vacuum fluctuations from intergalactic space towards stellar objects.

Flying far and fast: the distribution of distant hypervelocity star candidates from Gaia DR2 data

Context. Hypervelocity stars move fast enough to leave the gravitational field of their home galaxies and venture into intergalactic space. The most extreme examples known have estimated speeds in excess of 1000 km s−1. These can be easily induced at the centres of galaxies via close encounters between binary stars and supermassive black holes; however, a number of other mechanisms operating elsewhere can produce them as well. Aims. Recent studies suggest that hypervelocity stars are ubiquitous in the local Universe. In the Milky Way, the known hypervelocity stars are anisotropically distributed, but it is unclear why. Here, we used Gaia Data Release 2 (DR2) data to perform a systematic exploration aimed at confirming or refuting these findings. Methods. Our basic premise is that the farther the candidate hypervelocity stars are, the more likely they are to be unbound from the Galaxy. We used the statistical analysis of both the spatial distribution and kinematics of these objects to achieve our goals. Monte Carlo sampling techniques were applied to deal with large uncertainties. No global parallax zero-point correction was performed. Results. Focussing on nominal Galactocentric distances greater than 30 kpc, which are the most distant candidates, we isolated a sample with speeds in excess of 500 km s−1 that exhibits a certain degree of anisotropy but remains compatible with possible systematic effects. We find that the effect of the Eddington-Trumpler-Weaver bias is important in our case: over 80% of our sources are probably located further away than implied by their parallaxes; therefore, most of our velocity estimates are lower limits. If this bias is as strong as suggested here, the contamination by disc stars may not significantly affect our overall conclusions. Conclusions. The subsample with the lowest uncertainties shows stronger, but obviously systematic, anisotropies and includes a number of candidates of possible extragalactic origin and young age with speeds of up to 2000 km s−1.

КВАЗАРИ І РЕГЕНЕРАЦІЯ ВОДНЮ. ЧАСТИНА 1.

The burning out of hydrogen in stars leads to a decrease in its content and the gradual accumulation in galaxies of heavy chemical elements. In the conditions of the eternal existence of the Universe in galaxies there must be reverse processes that ensure the recycling of the waste of stars. The main product of the work of the relevant mechanisms should be hydrogen with a certain proportion of "metals". The emerging hydrogen, together with an admixture of other elements, contributes to the renewal of the stellar composition of the host galaxy. Its emissions outside the galaxy are already a condition for the creation in the intergalactic space of new stellar islands - small galaxies. Based on the analysis of observational data, galactic processes responsible for the processing of stellar baryon waste are shown. These processes begin with the work of gravitational forces, collecting matter available for processing in the center of the galaxy, and then a central supermassive galactic object can be connected to them. With good luck, a quasar is ignited in the center of the galaxy, which implements the second part of the reverse processes. Modern ideas about the central galactic body do not indicate the possibility of the existence of such processes. And this fact comes from the basic theory, the consequences of which sometimes exceed the capabilities of Nature in their practical implementation. The “painful”, but necessary for physics, revision of its individual positions allows the central supermassive “black hole” to be regarded as a dark Mitchell star - Laplace. The mechanisms associated with the processing of stellar waste, as well as some of the consequences of them. Some of the effects are among the observational data of quasars, and they are given below. But the main evidence - astronomical – is reflected in the second part of the article. It is suggested that the fate of the central body - the supermassive galactic nucleus. Under the conditions of the ever-existing Universe, this forecast indicates extremely rare, but the most ambitious events in the Metagalaxy - explosions in galactic nuclei.

КВАЗАРИ І РЕГЕНЕРАЦІЯ ВОДНЮ. ЧАСТИНА 2.

Further consequences of the mechanisms of hydrogen regeneration, which are realized in large galaxies during the period of activity of their nuclei, are considered. In addition to the indirect evidence presented in the first part and related to the work of the structures forming the jets, this part of the article considers direct evidence of the existence of these processes in galaxies. The evidence given is based on emissions of regenerated hydrogen into galactic and intergalactic space, as shown by astronomical observations of the Galaxy and its closest surroundings. Evidence is also found among the general observational data of intergalactic astronomy, the origin of which is well explained in the framework of the approach presented. However, these data are traditionally viewed through the prism of the dominant concept, that is, they are interpreted as residual hydrogen, which appeared from the Big Bang. Among the results of galactic astronomy there are data showing the possible contribution of the processes under consideration to the formation of the observable structure of the Milky Way, as well as their involvement in the organization of its satellite galaxies. The criterion is given, according to which galactic gas clouds and star groups can be distinguished, organized from the galaxy's own matter during the period of activity of its nucleus. Using the example of a spiral galaxy, it is suggested that the active galactic nuclei might be involved in the formation of the morphology of the galaxy. It is concluded that the central supermassive object in the period of its activity, performs its main galactic function - carries out the processing of waste of stars in the galaxy. This inverse process closes the chain of the continuous life cycle of the galaxy, which consists of two interrelated processes. The first process is the continuous burning of hydrogen in the stars, and the second is the episodic activity of the galactic nucleus, as a result of which hydrogen is recovered from the "waste", necessary to support direct stellar processes. One more process joins these two processes - the process of returning the energy expended by baryonic matter to electromagnetic radiation. It is realized through the dark component of matter. The main conclusion is made - the Universe as a system is well organized and self-sufficient for its eternal existence, and it does not need any external motivation.