The radio luminosity function and galaxy evolution of Abell 2256

Monthly Notices of the Royal Astronomical Society, 2007

We present a study of the stellar populations and morphologies of galaxies in the core of the galaxy cluster Abell 2218. Integral field spectroscopy (IFS) observations were performed using PMAS in the PPAK mode covering a field-of-view of ∼74"×64" centred on the core of the cluster, in order to obtain spectroscopy of an unbiased flux limited sample of cluster galaxies. Forty-three objects were detected in the IFS data, 31 of them with enough signal-to-noise to derive the redshift, all of them brighter than I <21.5 mag. Twenty-eight are at the redshift of the cluster (17 with previously unknown redshift). Individual spectra of the cluster members were extracted and compared with single stellar population models to derive the luminosity-weighted ages and metallicities. In addition, deep HST/ACS F475W, F555W, F625W and F850LP-band images centred on the cluster core were obtained from the HST archive (z lim ∼28 mag). A detailed morphological analysis of all the galaxies within the field-of-view of these images down to z lim <22.5 mag was performed classifying them as late-type, intermediate and early-type, on the basis of their Sérsic indices. The literature was scanned to look for spectroscopically confirmed cluster members located within the field-of-view of the ACS image. The final sample of 59 galaxies comprises our reported sample of 28 galaxies in the core, and 31 additional galaxies in the outer regions. In addition, multiband broad-band photometry was extracted from the literature for all objects.

2011

We performed WSRT observations of A2255 at 18, 21, 25, and 85 cm to understand the origin of its highly polarized radio halo and to study the 3-dimensional location of the different cluster features within the ICM. We analyzed the polarimetric data through rotation measure (RM) synthesis, producing three final RM cubes. The radio galaxies and the highly polarized filaments

Monthly Notices of the Royal Astronomical Society

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...

The Astronomical Journal, 1997

We present the results of our multiwavelength study of two nearby Abell clusters that contain extended tailed radio sources. From our analysis of archival PSPC X-ray data, VLA radio observations, and new velocity measurements, we find strong evidence that these clusters are not relaxed. Significant X-ray substructure is revealed by examining deviations from circular models of the overall X-ray surface brightness maps. We report 130 new redshifts from the fields of A578 and A1569 and find that 41 galaxies belong to A578 and 54 belong to A1569. Moreover, we detect the presence of substructure in the velocity and spatial distribution of galaxies. We identify two interacting subclusters in A578 and two gravitationally unbound subclusters in A1569. Furthermore, we find that the radio sources in A578 are at rest with respect to their subclusters and that the Wide-Angled Tailed (WAT) source in A1569 has a small peculiar motion with respect to its subcluster (220 km/s). The standard model of ram pressure induced jet curvature requires relative velocities of the radio sources with respect to the ICM of ∼ > 1000 km/s. Therefore, the apparent peculiar velocities of the radio galaxies can not explain the bending of the jets/tails for the Narrow-Angled Tailed (NAT) radio source in A578 and for the WAT in A1569. We suggest that a cluster-subcluster merger model provides a reasonable explanation for the X-ray and optical substructure detected in these systems.

Astronomy and Astrophysics, 2003

We derive the luminosity functions in three bands (BVR) for the rich galaxy cluster ABCG 209 at z=0.21. The data cover an area of ∼ 78 arcmin 2 in the B and R bands, while a mosaic of three pointings was obtained in the V band, covering an area of approximately 160 arcmin 2 . The galaxy sample is complete to B = 22.8 (N gal = 339), V = 22.5 (N gal = 1078) and R = 22.0 (N gal = 679).

Astronomy & Astrophysics, 2014

Context. We present a spectrophotometric analysis of the galaxy population in the area of the merging cluster Abell 2384 at z = 0.094. Aims. We investigate the impact of the complex cluster environment on galaxy properties, such as colour, morphology, and star formation rate. Methods. We combined multi-object spectroscopy from the 2dF and EFOSC2 spectrographs with optical imaging of the inner 30 × 30 arcmin of A2384 taken with the ESO Wide Field Imager. We carried out a kinematical analysis using the EMMIX algorithm and biweight statistics. We address the possible presence of cluster substructures with the Dressler-Shectman test. Cluster galaxies are investigated with respect to [OII] and Hα equivalent width. Galaxies covered by our optical imaging observations are additionally analysed in terms of colour, star formation rate, and morphological descriptors, such as Gini coefficient and M 20 index. We study cluster galaxy properties as a function of clustercentric distance and investigate the distribution of various galaxy types in colour−magnitude and physical space. Results. The Dressler-Shectman test reveals a substructure in the east of the 2dF field of view. We determine the mass ratio between the northern and southern subclusters to be 1.6:1. In accordance with other cluster studies, we find that a large number of the disk galaxies close to the cluster core show no detectable star formation (SF). Probably these are systems that are quenched by ram-pressure stripping. The sample of quenched disks populates the transition area between the blue cloud and the red sequence in colour−magnitude space. We also find a population of morphologically distorted galaxies in the central cluster region. Conclusions. The substructure east of A2384 might be a group of galaxies falling onto the main cluster. We speculate that our sample of quenched spirals represents an intermediate phase in the ram-pressure-driven transformation of infalling field spirals into cluster S0s. This is justified by their position in colour−magnitude space. The occurrence of morphologically distorted galaxies in the cluster core complies with the hypothesis of Abell 2384 representing a post merger system.

The Astronomical Journal, 2005

We analyze photometric properties of 1384 cluster galaxies as a function of the normalized distance to cluster center. These galaxies were selected in the central region (r/r 200 ≤ 0.8) of 14 southern Abell clusters chosen from the Southern Abell Cluster Redshifts Survey (SARS). For 507 of these galaxies we also obtained their luminosity profiles. We have studied the morphology-clustercentric distance relation on the basis of the shape parameter n of the Sérsic's law. We also have

Publications of the Astronomical Society of Japan, 2001

We discuss the properties of galaxies around the radio galaxy 3C 324 at z = 1.2 based on BV RIK ′ multi-band imaging data. We have applied a photometric-redshift technique to objects in the 3C 324 field, and identified 35 objects as plausible cluster members. We have found that red and luminous members are concentrated in a small region enclosed by a circle of 40 ′′ radius (0.33 Mpc at z = 1.2 for Ω 0 = 0.3, λ 0 = 0.7, H 0 = 70 km s −1 Mpc −1 cosmology) from the 3C 324 galaxy. The 3C 324 cluster is probably much more compact in size compared with the local clusters. We constructed a K ′-band luminosity function of the cluster members and fit a Schechter function, and found the characteristic magnitude to be K ′ * AB = 20.2 ± 0.6. This value is consistent with the extrapolation of the pure passive evolution seen for z < 1 clusters. We have identified eight bright galaxies which form a red color-magnitude sequence. The slope of the sequence is consistent with the passive evolution model down to K ′ AB < 22; we also found that there is no clear age variation in these bright red galaxies. However, seven out of these eight galaxies exhibit a significant excess in the rest UV light with respect to the passive evolution model. This may suggest that the massive early-type galaxies in this high-redshift cluster are still forming stars to some extent. We have confirmed a truncation of the color-magnitude sequence at K ′ AB ∼ 22; faint passively-evolving galaxies may not yet be present in this cluster at z ∼ 1.2. The overall color distribution of the cluster members, selected by the photometric redshift technique, is found to be very broad. We derived the fraction of blue galaxies in this cluster following a definition of Butcher and Oemler (1984), and obtained f B = 0.39 ± 0.28, which is higher than that for z < 1 clusters. This indicates that the star-formation activity of this cluster is, on the average, higher than that of lower redshift counterparts.

The Astrophysical Journal, 1995

A total of 663 galaxies with known redshifts in a 6 6 eld centered on A2634, including 211 new measurements, are used to study in detail the structure of the region. In it we nd six main galaxy concentrations: the nearby clusters A2634 and A2666, two groups in the vicinity of A2634, and two distant clusters at 18;000 (A2622) and 37;000 kms 1 seen in projection near the core of A2634. For A2634, the most richly sampled of those concentrations, we are able to apply strict cluster membership criteria. Two samples, |one containing 200 galaxies within two degrees from the cluster center and a second, magnitudelimited, of 118 galaxies within the central half degree|, are used to examine the 1 Work based in part on observations obtained at the Arecibo and Palomar Observatories. Observations at the Palomar Observatory were made as part of a continuing collaborative agreement b e t w een the

Astronomy and Astrophysics, 2001

We present a dynamical analysis of the galaxy cluster Abell 970 based on a new set of radial velocities measured at ESO, Pic du Midi and Haute-Provence observatories. Our analysis indicates that this cluster has a substructure and is out of dynamical equilibrium. This conclusion is also supported by differences in the positions of the peaks of the surface density distribution and X-ray emission, as well as by the evidence of a large scale velocity gradient in the cluster. We also found a discrepancy between the masses inferred with the virial theorem and with the X-ray emission, what is expected if the galaxies and the gas inside the cluster are not in hydrostatic equilibrium. Abell 970 has a modest cooling flow, as is expected if it is out of equilibrium as suggested by Allen (1998). We propose that cooling flows may have an intermittent behavior, with phases of massive cooling flows being followed by phases without significant cooling flows after the acretion of a galaxy group massive enough to disrupt the dynamical equilibrium in Send offprint requests to: D. Proust ⋆ based on observations made at ESO, La Silla (Chile), Haute-Provence and Pic du Midi Observatories (France) 2 L. Sodré Jr. et al.: The cluster of galaxies Abell 970. the center of the clusters. A massive cooling flow will be established again, after a new equilibrium is achieved. = 18, ∼ 75% at b cosmos J = 19, and ∼ 51% at b cosmos J = 19.75.