The dynamical status of ZwCl 2341.1+0000: a very elongated galaxy structure with a complex radio emission

We study the dynamical status of the galaxy system ZwCl 2341.1+0000, a filamentary multi-Mpc galaxy structure associated with a complex diffuse radio emission. Our analysis is mainly based on new spectroscopic data for 128 galaxies acquired at the TNG telescope. We also use optical data available in the SDSS and X-ray data from the Chandra archive. We select 101 cluster member galaxies and compute the cluster redshift ~0.2693 and the global LOS velocity dispersion ~1000 km/s. Our optical analysis agrees with the presence of at least three, likely four or more, optical subclusters causing the SSE-NNW elongation of the galaxy distribution and a significant velocity gradient in the S-N direction. In particular, we detect an important low-velocity subclump in the southern region, roughly coincident with the brightest peak of the diffuse radio emission but with a clear offset between the optical and radio peaks. We also detect one (or two) optical subcluster(s) at north, in correspondence with the second brightest radio emission, and another one in the central cluster region, where a third diffuse radio source has been recently detected. A more refined analysis involving the study of the 2D galaxy distribution suggests an even more complex structure. As for the X-ray analysis, we confirm the SSE-NNW elongation of the intracluster medium and detect four significant peaks. The X-ray emission is strongly asymmetric and offsetted with respect to the galaxy distribution, thus suggesting a merger caught in the phase of post-core-core passage. Our findings support two possible hypotheses for the nature of the diffuse radio emission of ZwCl 2341.1+0000: a 2 relics+halo scenario or diffuse emission associated with the infall and merging of several galaxy groups during the first phase of the cluster formation.Comment: 14 pages, 14 figures, 4 tables; MNRAS in pres

Internal dynamics of the galaxy cluster Abell 959

The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still being debated. In this paper we aim to obtain new insights into the internal dynamics of Abell 959, showing evidence of a diffuse radio source, analyzing velocities and positions of member galaxies. Our analysis is based on redshift data for 107 galaxies in the cluster field acquired at the Telescopio Nazionale Galileo. We also use photometric data from the Sloan Digital Sky Survey (Data Release 6). We combine galaxy velocities and positions to select 81 galaxies recognized as cluster members and determine global dynamical properties. We analyze the cluster searching for substructures by using several statistical methods. We also study the 2D galaxy distribution in the field of the cluster. We compare our results with those from X-ray and gravitational lensing analyses. We estimate a cluster redshift of z=0.2883 +/- 0.0004. We detect an NE high velocity group at 5' from the cluster center with a relative line--of--sight (LOS) velocity of ~ +1900 km/s with respect to the main system. We also detect a central, dense structure elongated along the SE--NW direction likely connected with the two dominant galaxies and their surrounding cores. This elongated central structure is probably the trace of an old cluster merger. The LOS velocity dispersion of galaxies is very high (1025 (-75/+104) km/s). The virial mass is M(<R=1.48 Mpc)= 1.15 (-0.19/+0.25) Msun. Our results suggest that this cluster is forming along two main directions of mass accretion and show the typical characteristics of radio clusters; i.e., it is very massive and shows a young dynamical state. However, deeper radio observations are needed to clarify the nature of the diffuse radio emission in Abell 959.Comment: 12 pages, 13 figures, 3 tables. Accepted for publication on Astronomy and Astrophysic

The puzzling merging cluster Abell 1914: new insights from the kinematics of member galaxies

We analyze the dynamical state of Abell 1914, a merging cluster hosting a radio halo, quite unusual for its structure. Our study considers spectroscopic data for 119 galaxies obtained with the Italian Telescopio Nazionale Galileo. We select 89 cluster members from spatial and velocity distributions. We also use photometry Canada-France-Hawaii Telescope archives. We compute the mean cluster redshift, =0.168, and the velocity dispersion which shows a high value, sigma_v=1210_{-110}^{+125} km/s. From the 2D analysis we find that Abell 1914 has a NE-SW elongated structure with two galaxy clumps, that mostly merge in the plane of the sky. Our best, but very uncertain estimate of the velocity dispersion of the main system is sigma_v~1000 km/s. We estimate a virial mass M_sys=1.4--2.6 10^{15} h_{70}^{-1} Msun for the whole system. We study the merger through a simple two-body model and find that data are consistent with a bound, outgoing substructure observed just after the core crossing. By studying the 2D distribution of the red galaxies, photometrically selected, we show that Abell 1914 is contained in a rich large scale structure, with two close companion galaxy systems, known to be at z~0.17. The system at SW supports the idea that the cluster is accreting groups from a filament aligned in the NE-SW direction, while that at NW suggests a second direction of the accretion NW-SE. We conclude that Abell 1914 well fits among typical clusters with radio halos. We argue that the unusual radio emission is connected to the complex cluster accretion and suggest that Abell 1914 resembles the well-known nearby merging cluster Abell 754 for its particular observed phenomenology.Comment: 14 pages, 10 figures, 2 table

Trade intensity and output synchronisation: On the endogeneity properties of the EMU

Using annual bilateral data over the period 1988-2011 for a panel of 24 industrialised and emerging economies, we analyse in a time-varying framework the determinants of output synchronisation in EMU (European Monetary Union) distinguishing between core and peripheral member states. The results support the specialisation paradigm rather than the endogeneity hypothesis. Evidence is found in the euro period of diverging patterns between the core and the peripheral EMU countries raising questions about the future stability of EMU

Evolution of zero-metallicity massive stars

We discuss the evolutionary properties of primordial massive and very massive stars, supposed to have formed from metal-free gas. Stellar models are presented over a large range of initial masses (8 Msun <= Mi <= 1000 Msun), covering the hydrogen- and helium-burning phases up to the onset of carbon burning. In most cases the evolution is followed at constant mass. To estimate the possible effect of mass loss via stellar winds, recent analytic formalisms for the mass-loss rates are applied to the very massive models (Mi >= 120 Msun).Comment: Invited talk at IAU Symp. 212, ``A Massive Star Odyssey, from Main Sequence to Supernova'', K.A. van der Hucht, A. Herrero, C. Esteban (eds.), 7 pages, 5 postscript figure

On Simulating Liouvillian Flow From Quantum Mechanics Via Wigner Functions

The interconnection between quantum mechanics and probabilistic classical mechanics for a free relativistic particle is derived in terms of Wigner functions (WF) for both Dirac and Klein-Gordon (K-G) equations. Construction of WF is achieved by first defining a bilocal 4-current and then taking its Fourier transform w.r.t. the relative 4-coordinate. The K-G and Proca cases also lend themselves to a closely parallel treatment provided the Kemmer- Duffin beta-matrix formalism is employed for the former. Calculation of WF is carried out in a Lorentz-covariant fashion by standard `trace' techniques. The results are compared with a recent derivation due to Bosanac.Comment: 9 pages, Latex; email: [email protected]

The structure of Abell 1351: a bimodal galaxy cluster with peculiar diffuse radio emission

We aim to review the internal structure and dynamics of the Abell 1351 cluster, shown to host a radio halo with a quite irregular shape. Our analysis is based on radial velocity data for 135 galaxies obtained at the Telescopio Nazionale Galileo. We combine galaxy velocities and positions to select 95 cluster galaxy members and analyse the internal dynamics of the whole cluster. We also examine X-ray data retrieved from Chandra and XMM archives. We measure the cluster redshift, =0.325, the line-of-sight (LOS) velocity dispersion, \sigma_v~1500 km/s, and the X-ray temperature, kT~9 keV. From both X-ray and optical data independently, we estimate a large cluster mass, in the 1--4 $10^{15}$ M$_\odot$ range. We attribute the extremely high value of \sigma_v to the bimodality in the velocity distribution. We find evidence of a significant velocity gradient and optical 3D substructure. The X-ray analysis also shows many features in favour of a complex cluster structure, probably supporting an ongoing merger of substructures in Abell 1351. The observational scenario agrees with the presence of two main subclusters in the northern region, each with its brightest galaxy (BCG1 and BCG2), detected as the two most important X-ray substructures with a rest-frame LOS velocity difference of \Delta v~2500 km/s (in the rest frame) and probably being in large part aligned with the LOS. We conclude that Abell 1351 is a massive merging cluster. The details of the cluster structure allow us to interpret the quite asymmetric radio halo as a `normal' halo plus a southern relic, strongly supporting a previous suggestion based only on inspection of radio and preliminary X-ray data.Comment: 13 pages, 13 figures, 1 tabl