4982623
The gas content of peculiar galaxies: Strongly interacting systems
A study of the gas content in 1038 interacting galaxies, essentially selected from Arp, Arp & Madore, Vorontsov-Velyaminov catalogues and some of the published literature, is presented here. The data on the interstellar medium have been extracted from a number of sources in the literature and compared with a sample of 1916 normal galaxies. The mean values for each of the different ISM tracers (FIR, 21 cm, CO lines, X-ray) have been estimated by means of survival analysis techniques, in order to take into account the presence of upper limits. From the data it appears that interacting galaxies have a higher gas content than normal ones. Galaxies classified as ellipticals have both a dust and gas content one order of magni- tude higher than normal. Spirals have in most part a normal dust and HI content but an higher molecular gas mass. The X-ray luminosity also appears higher than that of normal galaxies of same morphological type, both including or excluding AGNs. We considered the alternative possibilities that the molecular gas excess may derive from the existence of tidal torques which produce gas infall from the surrounding regions or from a different metallicity which affects the X conversion factor between the observed CO line luminosity and the H2 calculated mass. According to our tests, it appears that interacting galaxies possess a higher molecular mass than normal galaxies but with a similar star formation efficiency.
14891588
The visible environment of galaxies with counterrotation
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.
16975153
The bright galaxy population of five medium redshift clusters II. Quantitative galaxy morphology
Aims. Following the study presented in our previous paper, based on the Nordic Optical Telescope (NOT) sample, which consists of five clusters of galaxies within the redshift range 0.18 ≤ z ≤ 0.25 imaged in the central 0.5–2 Mpc in very good seeing conditions, we have studied the quantitative morphology of their bright galaxy population Methods. We analyzed the surface brightness profiles of the galaxy population in those clusters, after performing simulations in order to check the reliability of the fits. We also derived a quantitative morphological classification. Results. The structural parameters derived from these analyses are presented. We obtained that the structural parameters of E/S0 galaxies are similar to those shown by galaxies in low redshift clusters. However, the disc scales are different. In particular, the scales of the discs of galaxies in medium redshift clusters are statistically different than those located in similar galaxies in the Coma cluster. However, the scales of the discs of galaxies in medium redshift clusters are similar to nearby field galaxies. Conclusions. Our results suggest that the evolution of the disc component of galaxies in clusters is faster than in field ones. Mechanisms like galaxy harassment showing timescales of ∼1 Gyr could be responsible for this disc scale evolution. This indicates that spiral galaxies in clusters have undergone a strong evolution in the last 2.5 Gyr or that Coma is in some way anomalous.
119325667
The scaling relations of early{type galaxies in clusters ? I. Surface photometry in seven nearby clusters
This is the first paper of a series investigating the scaling relations of early–type galaxies in clusters. Here we illustrate the multi–band imagery and the image reduction and calibration procedures relative to the whole sample of 22 clusters at $0.05 \mathrel{\raise0.35ex\hbox{$\scriptstyle <$}\kern-0.6em \lower0.40ex\hbox{{$\scriptstyle \sim$}}}z \mathrel{\raise0.35ex\hbox{$\scriptstyle <$}\kern-0.6em \lower0.40ex\hbox{{$\scriptstyle \sim$}}}0.25$. We also present detailed surface photometry of 312 early–type galaxies in 7 clusters in the first redshift bin, $z \approx0.025$–0.075. We give for each galaxy the complete set of luminosity and geometrical profiles, and a number of global, photometric and morphological parameters. They have been evaluated taking into account the effects of seeing. Internal consistency checks and comparisons with data in the literature confirm the quality of our analysis. These data, together with the spectroscopic ones presented in the second paper of the series, will provide the local calibration of the scaling relations.
1840
Cluster formation in the LMC
In this work we present preliminary results concerning the properties of about 50 clusters and associations located in a densely populated region at the Southern edge of the supershell LMC~4. The ages of the clusters and associations are derived. The cluster formation rate peaks at about 10-20 Myr ago corresponding to the age of the formation of LMC~4. Objects younger than 10 Myr are located close to CO clouds, indicating a possible trigger of the recent star formation by the interaction of the supershell with the interstellar medium. 
Isophotal analysis has been done for 50% of the clusters. A large number of objects present isophotal distortions commonly interpreted as sign of interaction. Cluster multiplets are coeval within 20 Myr, suggesting a common origin. This indicates that clusters possibly form in large groups. Our findings are in agreement with the unified view of multi-scale star formation, where a size-duration correlation is expected.
18425047
The peculiar galaxy IC 1182: An ongoing merger?
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.
118188413
Disformal invariance of second order scalar-tensor theories: Framing the Horndeski action
The Horndeski action is the most general one involving a metric and a scalar field that leads to second order field equations in four dimensions. Being the natural extension of the well known Scalar-Tensor theories, its structure and properties are worth analysing along the experience accumulated in the latter context. Here we argue that disformal transformations play, for the Horndeski theory, a similar role to that of conformal transformations for Scalar-Tensor theories a l`a Brans-Dicke. We identify the most general transformation preserving second order field equations and discuss the issue of viable frames for this kind of theories, in particular the possibility to cast the action in the so called Einstein frame. Finally, we investigate the physical equivalence of such frames and their reciprocal relationship.
122241433
A Measurement of the Space - Like Pion Electromagnetic Form-Factor
Abstract The pion form factor has been measured in the space-like q 2 region 0.014 to 0.26 (GeV/ c ) 2 by scattering 300 GeV pions from the electrons of a liquid hydrogen target. A detailed description is given of the apparatus, data analysis and corrections to the data. The mean square charge radius extracted from the data is model-dependent. We find that a form which includes a realistic description of the form factor phase gives a similar results to the naive pole form, and conclude 〈r 2 π 〉 = 0.438±0.008 fm 2 .
44393741
PEP-N detector layout
We describe a possible experimental apparatus for a proposed new experiment to be carried out at an asymmetrical collider, consisting of the PEP-II Low Energy Ring (LER) and a new electron storage ring (Very Low Energy Ring, VLER) of energy 100 MeV < Ee < 800 MeV . The accessible center of mass (CM) energy will then be 1.2 GeV < √ s < 3.15 GeV . While there are many important physics measurements that are feasible at this collider, a lot of emphasis will be on R, the ratio of the hadron and muon pair cross sections, and on the determination of nucleon form factors. This paper is organized as follows: the main physics motivations will be outlined in section 2. The measurement method of R and the experimental requirements will be the subject of section 3, while the detector requirements will be discussed in section 4. Section 5 will be devoted to rates and running time. The detector layout will then be presented in section 6. The individual detector components will be briefly described in section 7 (a full description can be found in the dedicated papers in these proceedings). Finally in section 8 we will present our conclusions.
122440723
The barrel DIRC of the PANDA experiment
Abstract Cooled antiproton beams of unprecedented intensities in the energy range of 1–15 GeV/ c will be used at the P ¯ ANDA experiment at FAIR to perform high precision experiments in the charmed quark sector. The charged particle identification in the barrel region needs a thin detector operating in a strong magnetic field. Both requirements can be met by a Cherenkov detector using the DIRC principle. Combining the time of arrival of the photons with their spatial image determines not only the particles velocity, but also the wavelength of the photons. Therefore, dispersion correction at the lower and upper detection thresholds is possible. Special care has to be taken to couple the photon detector to the barrel radiator bars.
118676553
Experimental proposal to study the excess at Mjj=150 GeV presented by CDF at Fermilab
We propose an experimental test to verify the unexpected excess at Mjj=150GeV presented by the CDF collaboration in the invariant mass distribution of jet pairs produced in association with a W boson. 
We propose a formation experiment in which the energy range of the Mjj excess is scanned with proton-antiproton interactions at the Tevatron.