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

Ostanki velikih sesalcev holocenske starosti iz jame Stenašca/Grotta dell’Edera na Tržaškem Krasu (izkopavanja v letih 1990–2001)

The zooarchaeology and taphonomy of large mammal remains from Grotta dell’Edera (Trieste Karst, northern Italy) are presented in this paper. A Mesolithic (Sauveterrian) Preboreal assemblage testifies to a first human occupation, followed by a second longer Sauveterrian frequentation from the Boreal until the beginning of the Atlantic. The last Mesolithic groups are represented by a Castelnovian assemblage, in which the bones of domesticates were detected with wild games remains. The presence of weathered bones in this layer indicates possible slow sedimentation, which may have led to the formation of a palimpsest, but more geoarchaeological data are needed to clarify this context. Neolithic and Eneolithic layers are characterized by an overwhelming presence of caprines and by an increase in the domestic pig and cattle through time. A number of caprine foetal remains points to the presence of individuals accumulated due to natural death and to the caution needed in evaluating caprine age profiles from sites used as stables.Predstavljeni so rezultati zooarheološke in tafonomske analize ostankov velikih sesalcev iz jame Stenašca/Grotta dell’Edera) na Tržaškem Krasu. Najstarejše človekove sledi so datirane v mezolitik (sovterjen). Ljudje so se namreč v jami občasno zadrževali že v predborealu, intenzivneje pa so jo začeli obiskovati v borealu in v začetku atlantika. Zadnja faza prisotnosti mezolitskih skupin je časovno umeščena v kastelnovjen. Označujejo jo ostanki domačih in lovnih živali, pri čemer večji del kosti izkazuje sledi neposredne izpostavljenosti vremenskim pojavom. To bi lahko pričalo o razmeroma počasnem odlaganju omenjene plasti, ki je povzročilo nastanek palimpsesta, vendar bi dokončna razjasnitev problematike terjala več geoarheoloških podatkov. Za skupek živalskih ostankov iz neolitskih in eneolitskih plasti je značilna očitna prevlada kosti in zob drobnice, pa tudi postopna rast števila najdb domačega prašiča in goveda. Na podlagi prisotnosti posameznih kosti ovčjih in/ali kozjih zarodkov je mogoče sklepati na naraven pogin teh živali. Slednje kliče k previdnosti pri oceni starostnih profilov domestikatov z najdišč, ki so bila uporabljana kot staje

Structure and Evolution of Galaxy Clusters: Internal Dynamics of ABCG 209 at z~0.21

We study the internal dynamics of the rich galaxy cluster ABGC 209 on the basis of new spectroscopic and photometric data. The distribution in redshift shows that ABCG 209 is a well isolated peak of 112 detected member galaxies at z=0.209, characterised by a high value of the line-of-sight velocity dispersion, sigma_v=1250-1400 Km/s, on the whole observed area (1 Mpc/h from the cluster center), that leads to a virial mass of M=1.6-2.2x10^15 M_sun within the virial radius, assuming the dynamical equilibrium. The presence of a velocity gradient in the velocity field, the elongation in the spatial distribution of the colour-selected likely cluster members, the elongation of the X-ray contour levels in the Chandra image, and the elongation of cD galaxy show that ABCG 209 is characterised by a preferential NW-SE direction. We also find a significant deviation of the velocity distribution from a Gaussian, and relevant evidence of substructure and dynamical segregation. All these facts show that ABCG 209 is a strongly evolving cluster, possibly in an advanced phase of merging.Comment: 26 pages, 14 figures. A&A in pres

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

Multi-object spectroscopy of CL1821+643: a dynamically relaxed cluster with a giant radio halo?

We present the study of the dynamical status of the galaxy cluster CL1821+643, a rare and intriguing cool-core cluster hosting a giant radio halo. We base our analysis on new spectroscopic data for 129 galaxies acquired at the Italian Telescopio Nazionale Galileo. We also use spectroscopic data available from the literature and photometric data from the Sloan Digital Sky Survey. We select 120 cluster member galaxies and compute the cluster redshift \u2dc 0.296 and the global line-of-sight velocity dispersion \u3c3V \u2dc 1100 km s-1. The results of our analysis are consistent with CL1821+643 being a massive (M > 1015 M 99) dynamically relaxed cluster dominated by a big and luminous elliptical at the centre of the cluster potential well. None of the tests employed to study the cluster galaxies kinematics in the 1D (velocity information), 2D (spatial information), and 3D (combined velocity and spatial information) domains is able to detect significant substructures. While this picture is in agreement with previous results based on X-ray data and on the existence of the central cool core, we do not find any evidence of a merging process responsible for the radio halo discovered in this cluster. Thus, this radio halo remains an open problem that raises doubts about our understanding of diffuse radio sources in clusters

XMM-Newton temperature maps for five intermediate redshift clusters of galaxies

We have analyzed XMM-Newton archive data for five clusters of galaxies (redshifts 0.223 to 0.313) covering a wide range of dynamical states, from relaxed objects to clusters undergoing several mergers. We present here temperature maps of the X-ray gas together with a preliminary interpretation of the formation history of these clusters.Comment: 4 pages, 2 figs. Accepted for publication in the Proceedings of the 36th COSPAR Scientific Assembl