Shell galaxies as laboratories for testing MOND

Tests of MOND in ellipticals are relatively rare because these galaxies often lack kinematic tracers in the regions where the MOND effects are significant. Stellar shells observed in many elliptical galaxies offer a promising way to constrain their gravitational field. Shells appear as glowing arcs around their host galaxy. They are observed up to ~100 kpc. The stars in axially symmetric shell systems move in nearly radial orbits. The radial distributions of shell locations and the spectra of stars in shells can be used to constrain the gravitational potential of their host galaxy. The symmetrical shell systems, being especially suitable for these studies, occur in approximately 3% of all early-type galaxies. Hence the shells substantially increase the number of ellipticals in which MOND can be tested up to large radii. In this paper, we review our work on shell galaxies in MOND. We summarize the paper B\'{i}lek et al. (2013), where we demonstrated the consistency of shell radii in an elliptical NGC 3923 with MOND, and the work B\'{i}lek et al. (2014), in which we predicted a giant (~200 kpc), as yet undiscovered shell of NGC 3923. We explain the shell identification method, which was used in these two papers. We further describe the expected shape of line profiles in shell spectra in MOND which is very special due to the direct relation of the gravitational field and baryonic matter distribution (B\'{i}lek et al., 2014, in preparation).Comment: 21 pages, 8 figures, 1 table, accepted for publication in the special MOND issue of the Canadian Journal of Physic

Simulations of shell galaxies with GADGET-2: Multi-generation shell systems

As the missing complement to existing studies of shell galaxies, we carried out a set of self-consistent N-body simulations of a minor merger forming a stellar shell system within a giant elliptical galaxy. We discuss the effect of a phenomenon possibly associated with the galaxy merger simulations --- a presence of multiple generations of shells.Comment: 2 pages, 1 figure, to appear in the Proceedings of JENAM 2010, Symposium 2: "Environment and the formation of galaxies: 30 years later

Galaxie se slupkami: kinematika slupek, rozpad satelitní galaxie a dynamické tření

Název práce: Galaxie se slupkami: kinematika slupek, rozpad satelitní galaxie a dynamické tření Autor: Ivana Ebrová Katedra / Ústav: Astronomický ústav AV ČR, v.v.i. Vedoucí doktorské práce: RNDr. Bruno Jungwiert, Ph.D., Astronomický ústav AV ČR, v.v.i. Abstrakt: Slupky hvězdné povahy pozorované v mnoha eliptických a čočkových galaxiích, jakožto i v několika spirálních a trpasličích galaxiích jsou pravděpodobně pozůstatkem radiální galaktické srážky velké a malé galaxie. Ukazujeme, že distribuce rychlostí hvězd slupky ve směru zorného paprsku vykazuje čtyři jasná maxima. Našli jsme jednoduchý analytický předpis spojující polohy těchto maxim s tvarem potenciálu galaxie, jmenovitě s kruhovou rychlostí na poloměru slupky a rychlostí šíření slupky. Tento předpis s úspěchem aplikujeme na výsledky simulace radiální srážky galaxií s testovacími částicemi. Kinematika slupek se tedy může stát novým nezávislým nástrojem pro určení obsahu temné hmoty ve slupkových galaxiích až do vzdálenosti okolo 100 kpc od centra galaxie. Navíc zkoumáme dynamické tření a postupný rozpad kanibalizované galaxie během srážky produkující slupky v simulacích s testovacími částicemi. Kombinace těchto dvou efektů může značně přerozdělit polohy a jasnosti vzniklých slupek. Zanedbání těchto efektů může vést k závažným chybách při pokusu o...Title: Shell galaxies: kinematical signature of shells, satellite galaxy disruption and dynamical friction Author: Ivana Ebrová Department / Institute: Astronomical Institute of the Academy of Sciences of the Czech Republic Supervisor of the doctoral thesis: RNDr. Bruno Jungwiert, Ph.D., Astronomical Institute of the Academy of Sciences of the Czech Republic Abstract: Stellar shells observed in many giant elliptical and lenticular as well as a few spiral and dwarf galaxies presumably result from radial minor mergers of galaxies. We show that the line-of-sight velocity distribution of the shells has a quadruple-peaked shape. We found simple analytical expressions that connect the positions of the four peaks of the line profile with the mass distribution of the galaxy, namely, the circular velocity at the given shell radius and the propagation velocity of the shell. The analytical expressions were applied to a test-particle simulation of a radial minor merger, and the potential of the simulated host galaxy was successfully recovered. Shell kinematics can thus become an independent tool to determine the content and distribution of dark matter in shell galaxies up to ~100 kpc from the center of the host galaxy. Moreover we investigate the dynamical friction and gradual disruption of the cannibalized galaxy...Matematicko-fyzikální fakultaFaculty of Mathematics and Physic

Galaxies with kinematically distinct cores in Illustris

The growing amount of integral-field spectroscopic data creates an increased demand for understanding kinematic peculiarities that carry valuable information about the evolution of the host galaxies. For kinematically distinct cores (KDCs), a number of formation mechanisms have been proposed, but it is still unclear which of them commonly occur in the Universe. We aim to address the KDC formation in the cosmological context. We used the publicly available data of the large-scale hydrodynamic cosmological simulation Illustris. We identify 134 KDCs, study their properties, and follow their evolution back in time. Examples of four galaxies hosting KDCs are presented and described in detail. The masses of the KDC hosts follow the general distribution of the Illustris galaxies, with a possible slight preference towards massive galaxies. KDCs can be long-lived features, with their formation epochs roughly uniformly distributed in look-back times 0-11.4 Gyr, and they can survive even major or multiple subsequent mergers. There is no single channel of KDC formation, but mergers seem to be the formation mechanism for about 60% of KDCs with a significant preference for major mergers and with the percentage being higher among massive hosts. Other KDCs formed during a pericentric passage or flyby of another galaxy, by precession of a previously formed rapidly rotating core, or without an obvious external cause. The mean mass-weighted stellar age inside the KDC radius is either about the same as the look-back time of the KDC formation or older. Although the radii of our KDCs are on average larger than observed, we find that younger stellar ages are typically associated with smaller KDCs. A significant fraction of KDC hosts possess stellar shells formed during mergers that led to KDCs within the last 5 Gyr, or double peaks in their velocity dispersion maps.Comment: 18 pages, 16 figures, 1 table; accepted for publication in A&

Effect of Knee Injury on Foot Load of Rugby Players

Předmětem této práce je statistické vyhodnocení získaných dat pedobarometrického měření a zjištění jejich možné souvislosti s bolestí kolen u hráčů ragby. Nasbíraná data byla hodnocena dle různých kritérií a byly zohledněny výpovědi dotazníků, které zahrnovaly specifika bolesti kolen a úrazovou historii hráčů. Kontrolní soubor představovala zdravá končetina každého hráče, s níž byly výsledky porovnávány. V teoretické části práce se pojednává o základních anatomických, kineziologických a biomechanických aspektech sledovaných kloubů. Tato část práce také ozřejmuje obecnou etiologii zranění kolen a příčinu vzniku úrazů i v ragby, jehož představení náleží prvním stránkám práce. Metodika práce charakterizuje testovaný soubor a jeho sportovní nároky. Specifikuje pravidla a postupy provedeného pedobarometrického měření. Speciální část se věnuje interpretaci zjištěných výsledků a jejich diskuzi. Ze zjištěných hodnot dominuje umístění bodu maximálního tlaku a rozložení předozadního zatížení během chůze i stoje. Bod největšího tlaku náleží bolavé končetině a stejně tak předozadní zatížení je na sledované končetině výraznější na přední části nohy. Diskuze práce hodnotí získané výsledky a porovnává je se zahraničními autory a již proběhlými studiemi.The aim of this thesis is a statistical evaluation of the data gained from a pedobarometrical analysis and discovering their possible connection with knee pain in rugby players. The collected data were evaluated on the basis of various criteria together with the replies to questionnaires which included the specifics of knee pain and the player's injury history. All the results were compared with control samples - the non-injured limb of each player. In the theoretical framework of the thesis I deal with the basic anatomical, kinesiological and biomechanical aspects of the monitored joints. This part also includes clarification of the general etiology of knee injuries and rugby injury causes, as described on the first pages of the thesis. The methodology of work characterises the tested file and its sport demands. It specifies the rules and procedures of the made pedobarometrical measuring. The interpretation of the results and their discussion is analyzed in a special part of the thesis. Plantar peak pressure location and anteroposterior load distribution during walking and standing dominate from all the measured values. Just as the plantar peak pressure appertains to the painful limb, the anteroposterior load distribution is more distinct at the front part of the leg. The obtained results and their comparison with foreign authors and studies are evaluated in the thesis discussion

Deep imaging of the shell elliptical galaxy NGC3923 with MegaCam

Context. The elliptical galaxy NGC 3923 is known to be surrounded by a number of stellar shells, probable remnants of an accreted galaxy. Despite its uniqueness, the deepest images of its outskirts come from the 1980s. On the basis of the modified Newtonian dynamics (MOND), it has recently been predicted that a new shell lies in this region. Aims. We obtain the deepest image ever of the galaxy, map the tidal features in it, and search for the predicted shell. Methods. The image of the galaxy was taken by the MegaCam camera at the Canada-France-Hawaii Telescope in the g' band. It reached the surface-brightness limit of 29 mag/arcsec2. In addition, we reanalyzed an archival HST image of the galaxy. Results. We detected up to 42 shells in NGC 3923. This is by far the highest number among all shell galaxies. We present the description of the shells and other tidal features in the galaxy. A probable progenitor of some of these features was discovered. The shell system likely originates from two or more progenitors. The predicted shell was not detected, but the new image revealed that the prediction was based on incorrect assumptions and poor data.Comment: 14 pages, 2 tables, 19 figures, accepted for publication in A&

MOND implications for spectral line profiles of shell galaxies: shell formation history and mass-velocity scaling relations

Context. Many ellipticals are surrounded by round stellar shells probably stemming from minor mergers. A new method for constraining gravitational potential in elliptical galaxies has recently been suggested. It uses the spectral line profiles of these shells to measure the circular velocity at the edge of the shell and the expansion velocity of the shell itself. MOND is an alternative to the dark matter framework aiming to solve the missing mass problem. Aims. We study how the circular and expansion velocities behave in MOND for large shells. Methods. The asymptotic behavior for infinitely large shells is derived analytically. The applicability of the asymptotic results for finitely sized shells is studied numerically on a grid of galaxies modeled with S\'ersic spheres. Results. Circular velocity settles asymptotically at a value determined by the baryonic mass of the galaxy forming the baryonic Tully-Fisher relation known for disk galaxies. Shell expansion velocity also becomes asymptotically constant. The expansion velocities of large shells form a multibranched analogy to the baryonic Tully-Fisher relation, together with the galactic baryonic masses. For many - but not all - shell galaxies, the asymptotic values of these two types of velocities are reached under the effective radius. If MOND is assumed to work in ellipticals, then the shell spectra allow many details of the history to be revealed about the formation of the shell system, including its age. The results pertaining to circular velocities apply to all elliptical galaxies, not only those with shells.Comment: 8 pages, 7 figures, 1 table, accepted for publication in A&

N-body simulations of shell galaxies

Shell galaxies are ordinary elliptical galaxies that contain a fine structure in the form of concentric arcs with sharp edges in their luminous profile. This work contains a summary of our comprehensive study of the actual research and publications on this remarkable phenomenon, concerning both the observations as well as the numerical simulations. Along with it we present the results of our own simulations that broaden our view of the origin of the shells in a radial merger of a massive elliptical galaxy with a less massive one. We have introduced the dynamical friction into the simulation by semi-analytical means based on the Chandrasekhar formula. The main result is that the dynamical friction together with the gradual disintegration of the secondary galaxy that is also discussed can significantly affect the process of the shell formation and must be taken into consideration in their modelling. It turns out that the time scales on which the merger takes place are rather sensitive to the choice of the parameters. We present an estimate of their magnitude in different cases. The mass loss of the secondary galaxy during the merger mitigates the effect of the dynamical friction but does not make its role negligible.Astronomický ústav UKAstronomical Institute of Charles UniversityFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Auxiliary verbs in present-day Italian and German

Tato bakalářská práce se zabývá pomocnými slovesy v současné italštině a němčině. Je rozdělena na teoretickou a praktickou část. První kapitola teoretické části přináší definici pomocného slovesa a dále se zabývá pomocnými slovesy a jejich volbou v různých jazycích. Druhá kapitola pojednává o pomocných slovesech a jejich užití v italštině, zvláště se pak věnuje volbě pomocného slovesa. Třetí kapitola se zabývá pomocnými slovesy v němčině. Také zde je pozornost věnována především volbě pomocného slovesa. Čtvrtá kapitola přináší porovnání pomocných sloves a jejich užití v obou jazycích. V praktické části, kterou tvoří pátá kapitola, jsou analyzovány výsledky korpusové rešerše zaměřené na vybraná slovesa, u nichž dochází k volbě pomocného slovesa. K získání dat pro praktickou část byly použity korpusy Araneum Italicum Maius a Araneum Germanicum Maius.This bachelor thesis deals with auxiliary verbs in contemporary Italian and German languages. It is devided into two parts, the theoretical and practical one. The first chapter of the theoretical part discusses the definition of auxiliary verbs and inquires into the auxiliaries and their choice in various languages. The second chapter treats the axiliary verbs and their use in Italian, the emphasis is put on the choice of auxiliary verbs. The third chapter focuses on auxiliaries in German. The attention is again aimed especially to the choice of the auxiliary verbs. The fourth chapter brings a comparison between the auxiliaries and their use in both languages. In the practical part there is an analysis of corpus research focused on chosen verbs with auxiliary split. The source of the data for the practical part are the Araneum Italicum Maius and Araneum Germanicum Maius corpora.Ústav románských studiíInstitute of Romance StudiesFaculty of ArtsFilozofická fakult