The orbital structure of a tidally induced bar

Orbits are the key building blocks of any density distribution and their study helps us understand the kinematical structure and the evolution of galaxies. Here we investigate orbits in a tidally induced bar of a dwarf galaxy, using an $N$-body simulation of an initially disky dwarf galaxy orbiting a Milky Way-like host. After the first pericenter passage, a tidally induced bar forms in the stellar component of the dwarf. The bar evolution is different than in isolated galaxies and our analysis focuses on the period before it buckles. We study the orbits in terms of their dominant frequencies, which we calculate in a Cartesian coordinate frame rotating with the bar. Apart from the well-known x$_1$ orbits we find many other types, mostly with boxy shapes of various degree of elongation. Some of them are also near-periodic, admitting frequency ratios of 4/3, 3/2 and 5/3. The box orbits have various degrees of vertical thickness but only a relatively small fraction of those have banana (i.e. smile/frown) or infinity-symbol shapes in the edge-on view. In the very center we also find orbits known from the potential of triaxial ellipsoids. The elongation of the orbits grows with distance from the center of the bar in agreement with the variation of the shape of the density distribution. Our classification of orbits leads to the conclusion that more than $80 \%$ of them have boxy shapes, while only $8 \%$ have shapes of classical x$_1$ orbits.Comment: 15 pages, 15 figures, accepted for publication in Ap

Tidally induced bars in dwarf galaxies on different orbits around a Milky Way-like host

Bars in galaxies may develop through a global instability or due to an interaction with another system. We study bar formation in disky dwarf galaxies orbiting a Milky Way-like galaxy. We employ $N$-body simulations to study the impact of initial orbital parameters: the size of the dwarf galaxy orbit and the inclination of its disc with respect to the orbital plane. In all cases a bar develops in the center of the dwarf during the first pericenter on its orbit around the host. Between subsequent pericenter passages the bars are stable, but at the pericenters they are usually weakened and shortened. The initial properties and details of the further evolution of the bars depend heavily on the orbital configuration. We find that for the exactly prograde orientation, the strongest bar is formed for the intermediate-size orbit. On the tighter orbit, the disc is too disturbed and stripped to form a strong bar. On the wider orbit, the tidal interaction is too weak. The dependence on the disc inclination is such that weaker bars form in more inclined discs. The bars experience either a very weak buckling or none at all. We do not observe any secular evolution, possibly because the dwarfs are perturbed at each pericenter passage. The rotation speed of the bars can be classified as slow ($R_\mathrm{CR}/l_\mathrm{bar}\sim2-3$). We attribute this to the loss of a significant fraction of the disc's rotation during the encounter with the host galaxy.Comment: 17 pages, 14 figures, accepted to Ap

Kolokwium habilitacyjne dra Marka Sobczyka

Kolokwium habilitacyjne dra Marka Sobczyk

Bazyli Masciuch e il suo „Церковне право супруже […]”. Le prime note della ricerca

Wasyl Masciuch, the catholic of an Eastern Catholic Church of the Byzantine tradition, the doctor of the canon law, the professor of a seminary and the fi rst superior newly created on Lemkowszczyzna – for catholics of ruthenian rite – Apostolic Administrature. Masciuch’s work “Церковне право супруже” (Eastern Catholic Church Law) is drawing marital rights of the Greek-Catholic (uniate) Church of Ruthenian rite (ritus ruthenus). He is embracing – in great measure – in-depth analysis of the substantive law, at least concerning fragments appear the procedure law. The method of the work of the Author is undoubtedly source, and research base impressive. Ouch – the path shows every of analysed institu 186 Ewa Gajda tions the genesis, and he is making it referring to ancient laws (to the Roman law above all), to Corpus Iuris Canonici and to the more later canon law (including the papal law). Masciuch isn’t shunning, even for short, of comparisons to the law of the Orthodox Church of the Byzantine tradition. Placing source excerpts of the private law is a variety of the work – usually hungarian and austrian – analogous to individual issues of ecclesiastical marital rights of the Ruthenian Catholic Church. The work contains, apart from that, the affl uent set of templates for letters in matrimonial matters. Generally speaking “Церковне право супруже”, in the present science of canon law, it isn’t known at all. Presented work of Wasyl Masciuch, so far treated after stepmother’s, is deserving considerable interesting, requires in-depth and deepened analysis

Pomiędzy sacrilegium i ἀνδρομανία. Prawo justyniańskie w relacjach historiografów bizantyńskich

The Roman legislator regulated various sexual attitudes, according to him, morally reprehensible: fornication, adultery, prostitution, pedophilia, sodomy and homosexuality. Republican leges, and later imperial leges, concerned the problems connected with these phenomena. The Christian Roman emperors and Byzantine emperors paid particular attention to those problems. A significant extension of sources, necessary in the analysis of the problem, are the literal sources, and among them the Byzantine historiography of the 6th–12th centuries. The author focused on the issue of homosexuality in Justinian’s law. The analysis of the problem includes Byzantine historiography (Procopius of Caesarea, John Malalas, Theophane the Confessor, Simone Logoteta, Michael the Syrian, George Kedrenos, George Hamartolos, John Zonaras).Rzymski prawodawca regulował różne, jego zdaniem naganne moralnie zachowania seksualne. Ingerencja prawodawcza odnosiła się do seksualności obywateli i pozostałych członków społeczeństwa. Leges republikańskie, a potem imperialne, dotyczyły problemów związanych ze zjawiskami nierządu, cudzołóstwa, prostytucji, pedofilii, sodomii i homoseksualizmu. Znaczącym rozszerzeniem źródeł niezbędnych w analizie problemu są źródła literackie, a wśród nich historiografia bizantyńska VI–XII w. Autorka skoncentrowała się na problemie homoseksualizmu w prawie Justyniana I. W analizie problemu zostały uwzględnione dzieła kronikarzy bizantyńskich: Prokopiusza z Cezarei, Jana Malalasa, św. Teofana Wyznawcy, Szymona Logotety, Michała Syryjczyka, Grzegorza Kedrena, Grzegorza Hamartola, Jana Zonarasa

Recognizing Sets in Evolutionary Multiobjective Optimization, Journal of Telecommunications and Information Technology, 2012, nr 1

Among Evolutionary Multiobjective Optimization Algorithms (EMOA) there are many which find only Paretooptimal solutions. These may not be enough in case of multimodal problems and non-connected Pareto fronts, where more information about the shape of the landscape is required. We propose a Multiobjective Clustered Evolutionary Strategy (MCES) which combines a hierarchic genetic algorithm consisting of multiple populations with EMOA rank selection. In the next stage, the genetic sample is clustered to recognize regions with high density of individuals. These regions are occupied by solutions from the neighborhood of the Pareto set. We discuss genetic algorithms with heuristic and the concept of well-tuning which allows for theoretical verification of the presented strategy. Numerical results begin with one example of clustering in a single-objective benchmark problem. Afterwards, we give an illustration of the EMOA rank selection in a simple two-criteria minimization problem and provide results of the simulation of MCES for multimodal, multi-connected example. The strategy copes with multimodal problems without losing local solutions and gives better insight into the shape of the evolutionary landscape. What is more, the stability of solutions in MCES may be analyzed analytically