The promotion of astronomy itself and the various aspects of scientific research conducted at AO JU are important because the demand for such knowledge in society is very high and continues to grow. This is reflected, inter alia, by the huge popularity of public sky shows and scientific events such as Evenings with Stars. On the other hand, there is a need to encourage young people to engage in STEM education and to drawing people's attention to the problem of climate change. In this seminar, I will briefly cover the activities undertaken by AO in terms of promotion and popularization - during and after the 2020 pandemic lockdown.

Baikal Gigaton Volume Detector is currently the largest underwater neutrino telescope in the world. It is located in the south-western part of Lake Baikal. Currently, since 2016, it has been expanded in order to achieve the assumed volume of 1 cubic km. However, its history dates back to the early 1980s, when the first experimental structures were placed in the lake. Since 2016, members of the team from the Institute of Nuclear Physics PAN have been participating in the project, not only just by data analysis, but also actively participating in its development. One of the team members, Konrad Kopański, participates in the BGVD Winter Expeditions as one of the constructors of the telescope. This presentation will briefly present the history of the project, the subject of research, methods, but most of all the uniqueness of the project itself and unusual region where it is located.

Theoretical and numerical studies incorporating cosmic rays (CRs) into  global modeling of magnetized interstellar medium demonstrate that CRs  play an important role in the generation of large-scale galactic  magnetic fields, and, at the same time, in driving galactic winds.  CR-driven dynamos produce magnetic arms in galactic disks and  large-scale helical magnetic fields in galactic halos. These models,  however, often lack means to verify them via comparison with  observable data.
A possible solution to this problem comes with the recently introduced  and published ''Cosmic Ray Energy SPectrum'' (CRESP) module of PIERNIK  MHD code, being an implementation of energy-dependent propagation of  CR electrons. In this model, CR electrons propagate using the  energy-dependent diffusion-advection equation, including adiabatic  cooling and synchrotron losses.
The algorithm is used in global galactic disk simulation to study  propagation effects of CR electrons in edge-on disk galaxies and their  imprint on resulting synchrotron radiation. Synchrotron radiation maps  and slices are compared against observed radiation of NGC891 galaxy,  allowing direct comparison of a used model.
In the course of the simulation galactic magnetic field is magnified,  synthetic synchrotron radiation maps of simulated galaxies reproduce a  number of features observable in physical edge-on galaxies, e.g.  'X-shaped' polarization patterns and similar spectral slope of total  synchrotron emission. The disk, produces strong galactic wind is, with  outflow velocity comparable to NGC891, however showing the conical  shape and resulting in outflow-dominated emission, thus resembling  starburst galaxy M82.

The catalog of TeV gamma-ray emitting objects includes about 90 extragalactic sources, among which only a few belong to the class of radio galaxies or misaligned blazars. This smaller class includes PKS 0625-354, a source detected as a TeV gamma-ray emitter already in 2012. Here, we report H.E.S.S. observations of this active galaxy performed in November 2018. The classification of the object is still a matter of debate in the context of blazar and radio galaxy scenarios. With the recent H.E.S.S. observations, supported with multi-wavelength observations collected with Fermi-LAT, Swift-XRT, and Swift-UVOT, we report the detection of TeV gamma-ray variability of the sources. Ten days of H.E.S.S. observations revealed an outburst observed on November, 1st followed by a decrease of the gamma-ray flux. In this talk, I report the result of H.E.S.S. and multi-wavelength observations of PKS 0625-354. I also discuss the possible interpretation of the broadband spectral energy distribution of the source and the implication of the TeV gamma-ray variability detected.

Blazars are a rare class of active galactic nuclei (AGN) whose total radiative energy output is dominated by non-thermal processes; synchrotron (radio--to--optical frequencies) and inverse-Compton (IC; $\sim$X-ray--to--$\gamma-$ray frequencies) in a relativistic, non-stationary jet. In addition, blazars are also extremely variable on timescales ranging from decades to hours and even down to minutes. The power-law form of variability power spectral densities, $P(\nu_k)$ $=$ A $\nu_k^{-\beta}$, where $\nu_k$ is the temporal frequency, A is the normalization and $\beta$ is the slope, indicate that the variability is generated by the underlying {\it stochastic} processes which is of colored noise type (i.e., $\beta \simeq 1-3$). In this talk, I will summarize the results of our analysis using multiwavelength data sets at TeV (HESS and VERITAS), GeV ({\it Fermi}-LAT), X-ray ({\it Swift-}XRT and RXTE--PCA), multiband optical/infrared and radio (GHz band from MRO, UMRAO and OVRO programmes) frequencies covering a few decades to minutes timescales. The novelty of this study is that at optical frequency, by combining long-term (historical optical light curves) and densely sampled intra-night lightcurves, the PSD characteristics are investigated for temporal frequencies ranging over 6 orders of magnitude. Our main results are: (1) nature of processes driving the flux variability at synchrotron frequencies is different from those at IC frequencies ($\beta \sim $ 2 and 1, respectively); this could imply, that $\gamma-$ray variability, unlike the Synchrotron (radio-to-optical) one, is generated by the superposition of two stochastic processes with different relaxation timescales, (2) the main driver behind the optical variability is the same on years, months, days, and hours timescales ($\beta \sim 2$). Implications of these results are discussed in the context of commonly employed blazar emission models.

Cosmic rays, as produced in supernova remnants, have been shown to have a significant impact on galaxy evolution through their dynamical coupling with gas. They travel through advection and diffusion in the ISM, being accelerated by the magnetic field, and can easily escape galactic discs. This in turn translates into large outflows of gas, launching powerful galactic winds affecting the star formation, angular momentum and morphology of galaxies. In this seminar, I will present my work on the study of such winds using MHD + Nbody simulations of spiral galaxies including cosmic rays. Besides understanding the formation and evolution of cosmic ray driven winds, I am particularly interested in the influence of angular momentum on them, and therefore investigate and compare cosmic ray driven outflows for different angular momentum discs. Different amounts of angular momentum lead to different star formation rates, winds strengths, and disc morphologies. I will also show the winds angular momentum structure, as they are feeding from different regions of the disc, removing gas permanently from some areas while supplying others via galactic fountain mechanisms.

The perturbation theory in the context of cosmology is a difficult topic. Although linear perturbations are quite well understood, the higher-order contributions are not so easy to handle. Consideration of the perturbations beyond the linear order allows one to describe the larger amplitude of the inhomogeneities. This is important if one wants to know how the cosmological observables are affected by the large-scale structures in the Universe. In this talk, I will present the specific solution to the second-order perturbation theory around any FLRW cosmological model with a positive cosmological constant.

In this talk, I will report on my project in which I’m producing overlays of the radiation of galaxies in various spectral regimes onto the optical images that I am taking as an amateur astronomer at my private observatory. Since galaxies involve all kinds of astrophysical processes, they radiate essentially over the whole electromagnetic spectrum, from long-wavelength radio through gamma rays, including both continuum and spectral lines. Since we get to know all celestial objects with our human eyes in the first place, we use these optical images that are stored in our brains as a reference when studying galaxies at other wavelengths. This is important because our vision of galaxies goes along with an educated guess of the physical processes that the images disclose. It is only when we overlay data from other spectral regimes onto optical images that we start understanding what is going on in these objects. I will briefly present my observatory and equipment, explaining how the various overlays are produced and then present a series of instructive examples of isolated galaxies, pairs, groups, and clusters of galaxies. These overlays may be used when teaching undergraduate and graduate students, but also for public talks.

Astrophysical jets, launched from the immediate vicinity of accreting black holes, carry away large amounts of power in a form of bulk kinetic energy of jet particles and electromagnetic flux. In this talk I will introduce a simple analytical model for relativistic jets at larger distances from their launching sites, assuming a cylindrical axisymmetric geometry with a radial velocity shear and purely toroidal magnetic field. I will discuss its magnetization and ratio between the magnetic and gas pressures, as well as their relevance in the context of particle acceleration.

Through the analysis of radio continuum data from edge-on galaxies, we can gain a more comprehensive understanding of the influence of cosmic rays and galactic magnetic fields on the evolution of galaxies. Combining low- and high-frequency data sets, reveals the underlying transport mechanism of the cosmic ray electrons (CREs) and therefore gives insights into the galactic wind that is driven by stellar feedback. In this talk, I'll present the analysis of five edge-on galaxies with newly reduced data from VLA CHANG-ES L-band and LOFAR LoTSS DR2. With these data sets it is possible to double (compared to previous studies) the extent of the analysed synchrotron radio halos and therefore strongly increase the reliability of the analysis. Additionally, the transport mechanisms of CREs in these halos are analysed using a 1D cosmic ray transport model. The analysed radio halos show a large variety of wind velocities and the derived magnetic field strength profiles tend to agree with equipartition measurements. Furthermore, we find that the wind properties change when comparing central and outer parts of the galactic disks.

In my presentation I will describe the circumstances that stimulated Oort to study the cometary origin. I try to explain in which aspects of his theory he was correct and in which he was not. I show the main changes in the cometary origin understanding in the last 70 years. Finally I will try to answer the question: do the Oort cloud exist? Are there any evidences?