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.
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.
18924153
Substructures in WINGS clusters
Aims. We search for and characterize substructures in the projected distribution of galaxies observed in the wide field CCD images of the 77 nearby clusters of the Wide-field Nearby Galaxy-cluster Survey (WINGS). This sample is complete in X-ray flux in the redshift range 0.04 < z < 0.07. Methods. We search for substructures in WINGS clusters with DEDICA, an adaptive-kernel procedure. We test the procedure on Monte-Carlo simulations of the observed frames and determine the reliability for the detected structures. Results. DEDICA identifies at least one reliable structure in the field of 55 clusters. 40 of these clusters have a total of 69 substructures at the same redshift of the cluster (redshift estimates of substructures are from color-magnitude diagrams). The fraction of clusters with subelusters (73%) is higher than in most studies. The presence of subclusters affects the relative luminosities of the brightest cluster galaxies (BCGs). Down to L ∼ 10 11 L ⊙ , our observed differential distribution of subeluster luminosities is consistent with the theoretical prediction of the differential mass function of substructures in cosmological simulations.
18005599
On the Use of Scaling Relations for the Tolman Test
The use of relations between structural parameters of early-type galaxies to perform the Tolman test for the expansion of the universe is reconsidered. Scaling relations such as the fundamental plane or the Kormendy relation require the transformation from angular to metric sizes, to compare the relation at different z-values. This transformation depends on the assumed world model: galaxies of a given angular size, at a given z, are larger (in units of kiloparsecs) in a nonexpanding universe than in an expanding one. Furthermore, the luminosities of galaxies are expected to evolve with z in an expanding model. These effects are shown to conspire to reduce the difference between the predicted surface brightness (SB) change with redshift in the expanding and nonexpanding cases. We have considered expanding models with passive luminosity evolution. We find that their predictions for the visible photometric bands are very similar to those of the static model until z~1, and therefore the test cannot distinguish between the two world models. Recent good-quality data on the Kormendy relation and the fundamental plane at intermediate redshifts are consistent with the predictions from both models. In the K band, where the expected (model) luminosity evolutionary corrections are smaller, the differences between the expanding and static models amount to ~0.4 (0.8) mag at z=0.4 (1). It is shown that, owing to that small difference between the predictions in the covered z-range, and to the paucity and uncertainties of the relevant SB photometry, the existing K-band data are not adequate to distinguish between the different world metrics and cannot yet be used to discard the static case. It is pointed out that the scaling relations could still be used to rule out the nonevolving case if it could be shown that the coefficients change with the redshift.
118464591
A new photometric investigation of the double-ringed galaxy ESO 474—G26: unveiling the formation scenario
We present a detailed photometric study of the peculiar double-ringed galaxy ESO 474−G26. Near-infrared (NIR) and optical data have been used, with the main goal of constraining the formation history of ESO 474−G26. NIR photometry is fundamental in this kind of study, because it gives better constraints on the spectral energy distribution (SED) and traces the older stellar population of the galaxy well. This galaxy presents a very complex structure with two almost orthogonal rings, one in the equatorial and another in the polar plane, around an elliptical-like object. Due to the peculiar morphology of ESO 474−G26, we used both NIR images (J and K bands) to derive accurate analysis of the stellar light distribution and optical images (in the B, V and R bands) to derive colour profiles and colour maps to study the structure of the rings. The observational characteristics of ESO 474−G26 are typical of galaxies that have experienced some kind of interaction during their evolution. We investigated two alternatives: a merging process and an accretion event.
14261932
The evolution of the galactic morphological types in clusters
The morphological types of galaxies in nine clusters in the redshift range 0.1 < ∼ z < ∼ 0.25 are derived from very good seeing images taken at the NOT and the La Silla–Danish telescopes, with all galaxies at MV < −20 and within the central ∼1 Mpc 2 area being classified. With the purpose of investigating the evolution of the fraction of different morphological types with redshift, we compare our results with the morphological content of nine distant clusters studied by the MORPHS group (Dressler et al. 1997), five clusters observed with HST-WFPC2 at redshift z = 0.2− 0.3 (Couch et al. 1998), and Dressler’s (1980) large sample of nearby clusters. After having checked the reliability of our morphological classification both in an absolute sense and relative to the MORPHS scheme (Smail et al. 1997), we analyze the relative occurrence of elliptical, S0 and spiral galaxies as a function of the cluster properties and redshift. We find a large intrinsic scatter in the S0/E ratio, mostly related to the cluster morphology. In particular, in our cluster sample, clusters with a high concentration of ellipticals display a low S0/E ratio and, vice-versa, low concentration clusters have a high S0/E. At the same time, the trend of the morphological fractions (%Es, %S0s, %Sp) and of the S0/E and S0/Sp ratios with redshift clearly points to a morphological evolution: as the redshift decreases, the S0 population tends to grow at the expense of the spiral population, whereas the frequency of Es remains almost constant. We also analyze the morphology-density (MD) relation in our clusters and find that – similarly to higher redshift clusters – a good MD relation exists in the high-concentration clusters, while it is absent in the less concentrated clusters. Finally, the comparison of the MD relation in our clusters with that of the D97 sample suggests that the transformation of spirals into S0 galaxies becomes more efficient with decreasing local density. Subject headings: galaxies: clusters – galaxies: evolution – galaxies: structure
13240980
The PANDA Experiment at FAIR
The physics program of the future FAIR facility covers a wide range of topics that address central issues of strong interactions and QCD. The antiproton beam of unprecedented quality in the momentum range from 1 GeV/c to 15 GeV/c will allow the PANDA experiment to make high precision, high statistics measurements, which include charmonium and open charm spectroscopy, the search for exotic hadrons and the study of in-medium modifications of hadron masses.
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.
126084521
Measurements of the widths of charmonium states at the Fermilab anti-p accumulator ring
108986863
Performance measurements of histe-V VLPC photon detectors for E835 at FNAL
A set of 144 VLPC chips has been used by experiment E835 at FNAL for the readout of its scintillating fiber detector. During the data taking, the fibers have been exposed to rates up to 2.5×104 mips/sec, corresponding to 3.5×106 photons/sec on each VLPC pixel surface. This paper reports about a study on rate dependence of gain and quantum efficiency throughout the run, as well as VLPC failure statistics during operation. No significant aging effects are observed. A review about the overall system performance is given.
118368961
Non-minimally coupled dark matter: effective pressure and structure formation
We propose a phenomenological model in which a non-minimal coupling between gravity and dark matter is present in order to address some of the apparent small scales issues of ΛCDM model. When described in a frame in which gravity dynamics is given by the standard Einstein-Hilbert action, the non-minimal coupling translates into an effective pressure for the dark matter component. We consider some phenomenological examples and describe both background and linear perturbations. We show that the presence of an effective pressure may lead these scenarios to differ from ΛCDM at the scales where the non-minimal coupling (and therefore the pressure) is active. In particular two effects are present: a pressure term for the dark matter component that is able to reduce the growth of structures at galactic scales, possibly reconciling simulations and observations; an effective interaction term between dark matter and baryons that could explain observed correlations between the two components of the cosmic fluid within Tully-Fisher analysis.