In this paper we present a statistical study of the environments of 49 galaxies in which there is gas- or stellar- counterrotation. The number of possible companions in the field (to apparent ...magnitude 22), their size and concentration were considered. All the statistical parameters were analysed by means of Kolgomorov-Smirnov tests, using a control sample of 43 galaxies without counterrotation. From our data, no significant differences between the counter-rotating and control samples appear. This is different to Seyfert or radio-loud galaxies which lie in environments with a higher density of companions. On the contrary, if a weak tendency exists, for galaxies with gas counterrotation only, it is discovered in regions of space where the large scale density of galaxies is smaller. Our results tend to disprove the hypothesis that counterrotation and polar rings derive from a recent interaction with a small satellite or a galaxy of similar size. To a first approximation, they seem to follow the idea that all galaxies are born through a merger process of smaller objects occurring very early in their life, or that they derive from a continuous, non-traumatic infall of gas that formed stars later. Whatever the special machinery is which produces counterrotation or polar rings instead of a co-planar, co-rotating distribution of gas and stars, it seems not to be connected to the present galaxy density of their environments.
We report the first absolute measurement of the branching fraction of \(\Lambda^+_{c}\rightarrow \Lambda e^+\nu_e\). This measurement is based on 567 pb\(^{-1}\) of \(e^+e^-\) annihilation data ...produced at \(\sqrt{s}=4.599\) GeV, which is just above the \(\Lambda^+_c\bar{\Lambda}^-_c\) threshold. The data were collected with the BESIII detector at the BEPCII storage rings. The branching fraction is determined to be \(\mathcal B({\Lambda^+_c\rightarrow \Lambda e^+\nu_e})=(3.63\pm0.38({\rm stat})\pm0.20({\rm syst}))\%\), representing a more than twofold improvement in precision upon previously published results. As the branching fraction for \(\Lambda^+_{c}\rightarrow \Lambda e^+\nu_e\) is the benchmark for those of other \(\Lambda^+_c\) semileptonic channels, our result provides a unique test of different theoretical models, which is the most stringent to date.
Astron.Astrophys. 420 (2004) 873-879 A sample of isolated galaxies (IsG), selected by the ratio, $f$, between
inner and tidal forces acting upon a galaxy, is presented. The analysis of the
Coma ...cluster lead us to adopt the criterion $f\leq -4.5$ for IsG. The
candidates are from the CfA catalog with cz $\leq$5000 km/s, |b|> 40\deg, DEC
$\ge -$2.5\deg. The sample contains 203 objects from the initial 1706. We also
selected a sample (N=130) of perturbed galaxies, i.e., with companions (with
known z, $\Delta(cz)\le 500$ km/s), $f\geq-$2. The comparison of both samples
shows significant differences in morphology, size, mass, luminosity and colors.
Sc spirals are more frequent among IsG, and S0s among perturbed galaxies. IsG
appear to be smaller, less luminous and bluer than interacting objects. We also
found that bars are twice as frequent among perturbed galaxies in particular
for early S and S0. The perturbed galaxies have higher L$_{FIR}$/L$_B$ and
M$_{mol}$/L$_B$ ratios, but the atomic gas content is similar for the two
samples. The L-size and M-L relations shows similar trends, the main difference
being the almost total absence of big, bright and massive galaxies among the
IsG, and the almost total absence of small, faint and low mass galaxies among
the perturbed systems. The evolution induced by interactions, would therefore
proceed from late, small, faint and low mass S to earlier, bigger, more
luminous and more massive S and S0 galaxies, producing at the same time a
larger fraction of barred galaxies, but preserving the same relations between
global parameters. The properties of local IsG are similar to those of high
redshift galaxies, suggesting that the present day isolated galaxies could be
quietly evolved, unused {\sl building blocks} surviving in low density
environments.
A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The ...early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the \(B\)-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.
We studied the environment of a sample of galaxies in which the presence of polar rings or the presence of gas- and stars- counterrotation is observed. These galaxies are believed to have accreted ...this material, now in peculiar motion, from their environment. The variable considered here are the number of possible companions in the field, down to an apparent magnitude 22, their size, their concentration around the accreting galaxy, and a set of related parameters. A control sample of 'normal' galaxies has also been studied. From Kolgomorov-Smirnov tests of the considered variables, no significant differences have been found between the population of objects around the our accreting galaxies and the control sample. These results seems to give support to the models suggesting a long formation time for the acquisition process, starting from a diffuse gas instead of fagocitation of small satellite.
Broad and narrow band images and long slit spectroscopy of IC1182 are presented. The broad band images reveal a distorted morphology with a large, heavily obscured disk-like structure and several ...knots in the central region. Galactic material, some of it in the form of two tails, is detected well beyond the main body of the galaxy. The second, fainter tail and several knots are reported here for the first time. The narrow band images show that the galaxy is a powerful emitter. The emission in the main lines extends all over the galaxy, with plumes and arc-like structures seen in H\(\alpha\) at large distances from the center. The uncorrected H\(\alpha\) flux corresponds to 3.51\(\times10^{41}\) erg s\(^{-1}\), 3 times that of Arp 220. The internal extinction deduced from the Balmer decrement is high all along the slit, with E\(_{B-V}\approx\) 1. There are no clear signs of nuclear activity and the observed line ratios can be explained in terms of stellar photoionization. The metallicity of the gas in the two brightest central knots is low, 0.1 Z\(_{\odot}\) and 0.06 Z\(_{\odot}\) respectively. In the main body of the galaxy, besides the reported knots, the distribution of the ionized gas resembles that of an inclined disk about 12 kpc in size. The rotation pattern is complex and corresponds to two identifiable disk galaxies with observed rotation amplitudes of 200 \kms and 100 \kms respectively. The data presented here indicate that IC 1182 is a high luminosity starburst system, involving two systems in the process of merging, with two tidal tails emerging from the central region of the galaxy.
We know that the slope of the radial, stellar light distribution in galaxies is well described by an exponential decline and this distribution is often truncated at a break radius (\(R_{br}\)). We ...don't have a clear understanding for the origin of these outer truncations and several hypotheses have been proposed to explain them. We want to test the various theories with direct observations of the cold molecular gas for a few truncated galaxies in comparison with the non-truncated ones. The answer to the existence of a possible link between truncated stellar disks and the molecular gas density cannot be obtained from CO maps in the literature, because so far there are no galaxies with a clear truncation observed in CO at high resolution.
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