Quadruple-peaked spectral line profiles as a tool to constrain gravitational potential of shell galaxies

Stellar shells observed in many giant elliptical and lenticular as well as a few spiral and dwarf galaxies, presumably result from galaxy mergers. Line-of-sight velocity distributions of the shells could, in principle, if measured with a sufficiently high S/N, constitute one of methods to constrain the gravitational potential of the host galaxy. Merrifield & Kuijken (1998) predicted a double-peaked line profile for stationary shells resulting from a nearly radial minor merger. In this paper, we aim at extending their analysis to a more realistic case of expanding shells, inherent to the merging process, whereas we assume the same type of merger and the same orbital geometry. We use analytical approach as well as test particle simulations to predict the line-of-sight velocity profile across the shell structure. Simulated line profiles are convolved with spectral PSFs to estimate the peak detectability. The resulting line-of-sight velocity distributions are more complex than previously predicted due to non-zero phase velocity of the shells. In principle, each of the Merrifield & Kuijken (1998) peaks splits into two, giving a quadruple-peaked line profile, which allows more precise determination of the potential of the host galaxy and, moreover, contains additional information. We find simple analytical expressions that connect the positions of the four peaks of the line profile and 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. The shell kinematics can thus become an independent tool to determine the content and distribution of the dark matter in shell galaxies, up to ~100 kpc from the center of the host galaxy.Comment: 15 pages, 16 figures | v2: accepted for publication in A&A, minor language correction

MOND prediction of a new giant shell in the elliptical galaxy NGC 3923

Context. Stellar shells, which form axially symmetric systems of arcs in some elliptical galaxies, are most likely remnants of radial minor mergers. They are observed up a radius of ~100 kpc. The stars in them oscillate in radial orbits. The radius of a shell depends on the free-fall time at the position of the shell and on the time since the merger. We previously verified the consistency of shell radii in the elliptical galaxy NGC 3923 with its most probable MOND potential. Our results implied that an as yet undiscovered shell exists at the outskirts of the galaxy. Aims. We here extend our study by assuming more general models for the gravitational potential to verify the prediction of the new shell and to estimate its position. Methods. We tested the consistency of the shell radial distribution observed in NGC 3923 with a wide variety of MOND potentials of the galaxy. The potentials differed in the mass-to-light ratio and in distance to the galaxy. We considered different MOND interpolation functions, values of the acceleration constant a0, and density profiles of the galaxy. We verified the functionality of our code on a Newtonian self-consistent simulation of the formation of a shell galaxy. Results. Our method reliably predicts that exactly one new outermost shell exists at a galactocentric radius of about 1900′′ (~210 kpc) on the southwestern side of the galaxy. Its estimated surface brightness is about 28 mag arcsec-2 in B – a value accessible by current instruments. This prediction enables a rare test of MOND in an elliptical down to an acceleration of a0/ 10. The predictive power of our method is verified by reconstructing the position of the largest known shell from the distribution of the remaining shells

Ubiquitous signs of interactions in early-type galaxies with prolate rotation

Context. A small fraction of early-type galaxies (ETGs) show prolate rotation; that is, they rotate around their long photometric axis. In simulations, certain configurations of galaxy mergers are known to produce this type of rotation. Aims. We investigate the association of prolate rotation and signs of galaxy interactions among the observed galaxies. Methods. We collected a sample of 19 nearby ETGs with distinct prolate rotation from the literature and inspected their ground-based deep optical images for interaction signs – 18 in archival images and 1 in a new image obtained with the Milanković telescope. Results. Tidal tails, shells, disturbed asymmetric stellar halos, or ongoing interactions are present in all the 19 prolate rotators. Comparing this with the frequency of tidal disturbance among the general sample of ETGs of a roughly similar mass range and surface-brightness limit, we estimate that the chance probability of such an observation is only 0.00087. We also find a significant overabundance of prolate rotators that are hosting multiple stellar shells. The visible tidal features imply a relatively recent galaxy interaction. That agrees with the Illustris large-scale cosmological hydrodynamical simulation, where prolate rotators are predominantly formed in major mergers during the last 6 Gyr. In the appendix, we present the properties of an additional galaxy, NGC 7052, a prolate rotator for which no deep images are available, but for which an HST image revealed the presence of a prominent shell, which had not been reported before

Urinary iodine concentrations of pregnant women before delivery

Cíl: Srovnání jodurie těhotných žen před porodem s doporučenými hodnotami, referovanou substitucí a jodovým stavem jejich novorozenců. Metody: V letech 2008–2013 byly vyšetřeny jodurie 66 těhotných před porodem a 56 novorozenců 3. den po porodu. Výsledky byly srovnány s doporučenou normou, jodurie těhotných s hodnotami novorozenců, proběhla analýza nálezů ve vztahu k referované dávce jodu a analýza kolísání jodurie v průběhu dne. Výsledky: Suplementaci před porodem neužívalo 32 % těhotných. Z těhotných, které přípravky s jodem užívaly, mělo 38 % optimální dávku jodu 150 μg/den. Rozdíly v jodurii těhotných v závislosti na referované dávce jodu jsme neprokázali. Novorozenci těhotných se suplementací měli medián jodurie 3. den života nad 100 μg/l. V souboru se neprokázala období dne, kdy by těhotné měly významně vyšší nebo naopak nižší jodurie. Závěry: Suplementace jodem v těhotenství zlepšuje jodový stav novorozencůObjective: To compare urinary iodine concentrations (UIC) in pregnant women before delivery with the recommended UIC values, reported iodine supplementation during pregnancy, iodine status of their newborns and UIC diurnal fluctuations in pregnant women in the study. Methods: In the years 2008-2013, UIC in 66 pregnant women before delivery and UIC in 56 newborns on the 3rd day of life were examined. The results were compared with the recommended UIC values and their relation to the reported iodine supplementation was analyzed. Results: Thirty-two percent of pregnant women did not use any iodine supplementation during pregnancy. The optimum daily dose of 150 μg- was taken by thirty-eight percent of the pregnant women out of those who reported any form of iodine supplementation. The difference in UIC level results of pregnant women before delivery in relation to iodine supplementation was not statistically significant in our sample. In the group of women with iodine supplementation, newborns had median UIC levels above 100 μg-/l on the third day of life. There was no evidence of the effect of iodine supplementation on the fluctuations of maternal UIC levels during the day. Conclusion: Iodine supplemetation in pregnancy improves the iodine status of newborn

Substellar companions in low-mass eclipsing binaries

Aims. As part of our long-term observational project we aim to measure very precise mid-eclipse times for low-mass eclipsing binaries, which are needed to accurately determine their period changes. Over two hundred new precise times of minimum light recorded with CCD were obtained for three eclipsing binaries with short orbital periods: NSVS 01286630 (\hbox{P = 0\fd38}), NSVS 02502726 (\hbox{0\fd56}), and NSVS 07453183 (\hbox{0\fd37}). Methods. O−C diagrams of studied stars were analysed using all reliable timings, and new parameters of the light-time effect were obtained. Results. We derived for the first time or improved the very short orbital periods of third bodies of between one and seven years for all measured low-mass systems. We calculated that the lowest masses of the third components are between those of red and brown dwarfs. The multiplicity of these systems also plays an important role in the precise determination of their physical parameters. This research is part of an ongoing collaboration between professional astronomers and the Czech Astronomical Society, Variable Star and Exoplanet Section