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One of the challenges in understanding the quenching processes for galaxies is connecting progenitor star-forming populations to their descendant quiescent populations over cosmic time. Here we attempt a novel approach to this challenge by assuming that the underlying stellar mass distribution of galaxies is not significantly altered during environmental quenching processes that solely affect the gas content of cluster galaxies, such as strangulation and ram-pressure stripping. Using the deep, high-resolution photometry of the Hubble Frontier Fields, we create resolved stellar mass maps for both cluster and field galaxies, from which we determine 2D Sérsic profiles, and obtain Sérsic indices and half-mass radii. We classify the quiescent cluster galaxies into disk-like and bulge-like populations based on their Sérsic indices, and find that bulge-like quiescent galaxies dominate the quiescent population at higher masses ($M_\star > 10^{9.5}M_\odot$), whereas disk-like quiescent galaxies dominate at lower masses ($10^{8.5}M_\odot< M_\star < 10^{9.5}M_\odot$). Using both the Sérsic indices and half-mass radii, we identify a population of quiescent galaxies in clusters that are "morphological analogues" of field star-forming galaxies. These analogues are interpreted to be star-forming galaxies that had been environmentally quenched. We use these morphological analogues to compute the environmental-quenching efficiency, and we find that the efficiency decreases with increasing stellar mass. This demonstrates that environmental quenching is more effective on less massive galaxies and that the effect of environment on quenching galaxies is not completely separable from the effect of mass on quenching galaxies., 25 pages, 14 figures, accepted for publication in ApJ Revision ver. 1: Replaced title, fixed link to section 3

Galaxy evolution is driven by a variety of physical processes that are predicted to proceed at different rates for different dark matter haloes and environments across cosmic times. A record of this evolution is preserved in galaxy stellar populations, which we can access using absorption-line spectroscopy. Here we explore the large LEGA-C survey (DR3) to investigate the role of the environment and stellar mass on stellar populations at z ∼ 0.6–1 in the COSMOS field. Leveraging the statistical power and depth of LEGA-C, we reveal significant gradients in D n 4000 and Hδ equivalent widths (EWs) distributions over the stellar mass versus environment 2D spaces for the massive galaxy population (M > 1010 M ⊙) at z ∼ 0.6–1.0. D n 4000 and Hδ EWs primarily depend on stellar mass, but they also depend on environment at fixed stellar mass. By splitting the sample into centrals and satellites, and in terms of star-forming galaxies and quiescent galaxies, we reveal that the significant environmental trends of D n 4000 and Hδ EW, when controlling for stellar mass, are driven by quiescent galaxies. Regardless of being centrals or satellites, star-forming galaxies reveal D n 4000 and Hδ EWs, which depend strongly on their stellar mass and are completely independent of the environment at 0.6 < z < 1.0. The environmental trends seen for satellite galaxies are fully driven by the trends that hold only for quiescent galaxies, combined with the strong environmental dependency of the quiescent fraction at fixed stellar mass. Our results are consistent with recent predictions from simulations that point toward massive galaxies forming first in overdensities or the most compact dark matter haloes.

Context: The shape of the mass density profiles of cosmological halos informs us of the nature of DM and DM-baryons interactions. Previous estimates of the inner slope of the mass density profiles of clusters of galaxies are in opposition to predictions derived from numerical simulations of CDM. Aims: We determine the inner slope of the DM density profile of a massive cluster of galaxies, Abell S1063 (RXC J2248.7$-$4431) at $z=0.35$, with a dynamical analysis based on an extensive spectroscopic campaign carried out with the VIMOS and MUSE spectrographs at the ESO VLT. This new data set provides an unprecedented sample of 1234 spectroscopic members, 104 of which are located in the cluster core (R < 200 kpc), extracted from the MUSE integral field spectroscopy. The latter also allows the stellar velocity dispersion profile of the brightest cluster galaxy (BCG) to be measured out to 40 kpc. Methods: We used an upgraded version of the MAMPOSSt technique to perform a joint maximum likelihood fit to the velocity dispersion profile of the BCG and to the velocity distribution of cluster member galaxies over a radial range from 1 kpc to the virial radius (~ 2.7 Mpc). Results: We find a value of $\gamma_{DM} =0.99 \pm 0.04$ for the inner logarithmic slope of the DM density profile after marginalizing over all the other parameters. The newly determined dynamical mass profile is found to be in excellent agreement with the mass density profiles obtained from the independent X-ray hydrostatic analysis based on deep Chandra data, as well as the strong and weak lensing analyses. Our value of \gamma_{DM} is in very good agreement with predictions from cosmological CDM simulations. We will extend our analysis to more clusters in future works. If confirmed on a larger cluster sample, our result makes this DM model more appealing than alternative models., Comment: Accepted on Astronomy and Astrophysics

The stellar mass assembly of brightest cluster galaxies (BCGs) is still debated. We have observed in CO with the IRAM-30m two star forming BCGs belonging to SpARCS clusters, 3C 244.1 ($z=0.4$) and SDSS J161112.65+550823.5 ($z=0.9$), and compared their molecular gas and star formation properties with those of a compilation of $\sim100$ distant cluster galaxies, including nine additional distant BCGs at ${z\sim0.4-3.5}$. We have set robust upper limits of $M_{{\rm H}_2}, Comment: 18 pages, 4 figures, accepted for publication in A&A

We investigate the role of dense megaparsec-scale environments in processing molecular gas of cluster galaxies as they fall into the cluster cores. We selected a sample of ∼20 luminous infrared galaxies (LIRGs) belonging to intermediate-redshift clusters, mainly from the Herschel Lensing Survey and the Local Cluster Substructure Survey. These galaxies include MACS J0717.5+3745 at z = 0.546 and Abell 697, 963, 1763, and 2219 at z = 0.2 − 0.3. We performed spectral energy distribution modeling from the far-infrared to ultraviolet of the LIRGs, which span cluster-centric distances within r/r200 ≃ 0.2 − 1.6. We observed the LIRGs in CO(1→0) or CO(2→1) with the Plateau de Bure interferometer and its successor NOEMA, as part of five observational programs carried out between 2012 and 2017. We compared the molecular gas to stellar mass ratio M(H2)/M⋆, star formation rate (SFR), and depletion time (τdep) of the LIRGs with those of a compilation of cluster and field star-forming galaxies from the literature. The targeted LIRGs have SFR, M(H2)/M⋆, and τdep that are consistent with those of both main-sequence (MS) field galaxies and star-forming galaxies from the comparison sample. However we find that the depletion time, normalized to the MS value, tentatively increases with increasing r/r200, with a significance of 2.8σ, which is ultimately due to a deficit of cluster-core LIRGs with τdep ≳ τdep, MS. We suggest that a rapid exhaustion of the molecular gas reservoirs occurs in the cluster LIRGs and is indeed effective in suppressing their star formation and ultimately quenching them. This mechanism may explain the exponential decrease of the fraction of cluster LIRGs with cosmic time. The compression of the gas in LIRGs, possibly induced by intra-cluster medium shocks, may be responsible for the short timescales that are observed in a large fraction of cluster-core LIRGs. Some of our LIRGs may also belong to a population of infalling filament galaxies.

We present the brightest cluster galaxies (BCGs) catalog for SPectroscoic IDentification of eROSITA Sources (SPIDERS) DR14 cluster program value-added catalog. We list the 416 BCGs identified as part of this process, along with their stellar mass, star formation rates (SFRs), and morphological properties. We identified the BCGs based on the available spectroscopic data from SPIDERS and photometric data from SDSS. We computed stellar masses and SFRs of the BCGs on the basis of SDSS, WISE, and GALEX photometry using spectral energy distribution fitting. Morphological properties for all BCGs were derived by Sersic profile fitting using the software package SIGMA in different optical bands (g,r,i). We combined this catalog with the BCGs of galaxy groups and clusters extracted from the deeper AEGIS, CDFS, COSMOS, XMM-CFHTLS, and XMM-XXL surveys to study the stellar mass-halo mass relation using the largest sample of X-ray groups and clusters known to date. This result suggests that the mass growth of the central galaxy is controlled by the hierarchical mass growth of the host halo. We find a strong correlation between the stellar mass of BCGs and the mass of their host halos. This relation shows no evolution since z similar to 0.65. We measure a mean scatter of 0.21 and 0.25 for the stellar mass of BCGs in a given halo mass at low (0.1

We apply four statistical learning methods to a sample of $7941$ galaxies ($z, 30 pages, 21 figures, accepted for publication in MNRAS

About 35 years ago a class of galaxies with unusually strong Balmer absorption lines and weak emission lines was discovered in distant galaxy clusters. These objects, alternatively referred to as post-starburst, E+A or k+a galaxies, are now known to occur in all environments and at all redshifts, with many exhibiting compact morphologies and low-surface brightness features indicative of past galaxy mergers. They are commonly thought to represent galaxies that are transitioning from blue to red sequence, making them critical to our understanding of the origins of galaxy bimodality. However, recent observational studies have questioned this simple interpretation. From observations alone, it is challenging to disentangle the different mechanisms that lead to the quenching of star formation in galaxies. Here we present examples of three different evolutionary pathways that lead to galaxies with strong Balmer absorption lines in the EAGLE simulation: classical blue-to-red quenching, blue-to-blue cycle and red-to-red rejuvenation. The first two are found in both post-starburst galaxies and galaxies with truncated star formation. Each pathway is consistent with scenarios hypothesised for observational samples. The fact that 'post-starburst' signatures can be attained via various evolutionary channels explains the diversity of observed properties, and lends support to the idea that slower quenching channels are important at low redshift., Published in Nature Astronomy, 25th March 2019 (submitted version available on arxiv only). The final accepted version is available for all to read here https://rdcu.be/bsQIC. Corresponding author: V. Wild. 11 pages, 4 figures

Based on HST and MUSE data, we probe the stellar and gas properties (i.e. kinematics, stellar mass, star formation rate) of the radio-loud brightest cluster galaxy (BCG) located at the centre of the X-ray luminous cool core cluster Abell 2667 (z = 0.2343). The bi-dimensional modelling of the BCG surface brightness profile reveals the presence of a complex system of substructures extending all around the galaxy. Clumps of different size and shape plunged into a more diffuse component constitute these substructures, whose intense 'blue' optical colour hints to the presence of a young stellar population. Our results depict the BCG as a massive (M_star ~ 1.38 x 10^11 M_sun) dispersion-supported spheroid (v_star < 150 km/s, sigma_0 ~ 216 km/s) hosting an active supermassive black hole (M_SMBH ~ 3.8 x 10^9 M_sun) whose optical features are typical of low ionisation nuclear emission line regions. Although the velocity pattern of the stars in the BCG is irregular, the stellar kinematics in the regions of the clumps show a positive velocity of ~ 100 km/s, similarly to the gas component. An analysis of the mechanism giving rise to the observed lines in the clumps through empirical diagnostic diagrams points out that the emission is composite, suggesting the contribution from both star formation and AGN. We conclude our analysis describing how scenarios of both chaotic cold accretion and merging with a gas-rich disc galaxy can efficaciously explain the phenomena the BCG is undergoing., Accepted for publication on the 10th of June 2019 (MNRAS)

Context. Probing both star formation history and evolution of distant cluster galaxies is essential to evaluate the effect of dense environment on shaping the galaxy properties we observe today., Aims. We investigate the effect of cluster environment on the processing of the molecular gas in distant cluster galaxies. We study the molecular gas properties of two star-forming galaxies separated by 6 kpc in the projected space and belonging to a galaxy cluster selected from the frac Shallow Cluster Survey, at a redshift z = 1.2, that is,similar to 2 Gyr after the cosmic star formation density peak. This work describes the first CO detection from 1 < z < 1.4 star-forming cluster galaxies with no clear reported evidence of active galactic nuclei., Methods. We exploit observations taken with the NOEMA interferometer at similar to 3 mm to detect CO(2-1) line emission from the two selected galaxies, unresolved by our observations., Results. Based on the CO(2-1) spectrum, we estimate a total molecular gas mass M(H-2) = (2.2(-0.4)(+0.5)) x 10(10) M-circle dot, where fully excited gas is assumed, and a dust mass M-dust < 4.2 x 10(8) M(circle dot )for the two blended sources. The two galaxies have similar stellar masses and H alpha-based star formation rates (SFRs) found in previous work, as well as a large relative velocity of similar to 400 km s(-1) estimated from the CO(2-1) line width. These findings tend to privilege a scenario where both sources contribute to the observed CO(2-1). Using the archival Spitzer MIPS flux at 24 mu m we estimate an SFR (24 mu m) = (24(-8)(+12)) M-circle dot/yr for each of the two galaxies. Assuming that the two sources contribute equally to the observed CO(2-1), our analysis yields a depletion timescale of tau(dep) = (3.9(-1.8)(+1.4)) x 10(8) yr, and a molecular gas to stellar mass ratio of 0.17 +/- 0.13 for each of two sources, separately. We also provide a new, more precise measurement of an unknown weighted mean of the redshifts of the two galaxies, z = 1.163 +/- 0.001., Conclusions. Our results are in overall agreement with those of other distant cluster galaxies and with model predictions for main sequence (MS) field galaxies at similar redshifts. The two target galaxies have molecular gas mass and depletion times that are marginally compatible with, but smaller than those of MS field galaxies, suggesting that the molecular gas has not been sufficiently refueled. We speculate that the cluster environment might have played a role in preventing the refueling via environmental mechanisms such as galaxy harassment, strangulation, ram-pressure, or tidal stripping. Higher-resolution and higher-frequency observations will enable us to spatially resolve the two sources and possibly distinguish between different gas processing mechanisms.

We report direct evidence of pre-processing of the galaxies residing in galaxy groups falling into galaxy clusters drawn from the Local Cluster Substructure Survey (LoCuSS). 34 groups have been identified via their X-ray emission in the infall regions of 23 massive ($\rm \langle M_{200}\rangle = 10^{15}\,M_{\odot}$) clusters at $0.15, Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letters

We study the intra-cluster magnetic field in the poor galaxy cluster Abell 194 by complementing radio data, at different frequencies, with data in the optical and X-ray bands. We analyze new total intensity and polarization observations of Abell 194 obtained with the Sardinia Radio Telescope (SRT). We use the SRT data in combination with archival Very Large Array observations to derive both the spectral aging and Rotation Measure (RM) images of the radio galaxies 3C40A and 3C40B embedded in Abell 194. The optical analysis indicates that Abell 194 does not show a major and recent cluster merger, but rather agrees with a scenario of accretion of small groups. Under the minimum energy assumption, the lifetimes of synchrotron electrons in 3C40B measured from the spectral break are found to be 157 Myrs. The break frequency image and the electron density profile inferred from the X-ray emission are used in combination with the RM data to constrain the intra-cluster magnetic field power spectrum. By assuming a Kolmogorov power law power spectrum, we find that the RM data in Abell 194 are well described by a magnetic field with a maximum scale of fluctuations of Lambda_max=64 kpc and a central magnetic field strength of =1.5 microG. Further out, the field decreases with the radius following the gas density to the power of eta=1.1. Comparing Abell 194 with a small sample of galaxy clusters, there is a hint of a trend between central electron densities and magnetic field strengths., Comment: Accepted by Astronomy and Astrophysics, 29 pages, 15 figures. Abstract abridged. A pdf version with high-quality figures can be downloaded from http://erg.oa-cagliari.inaf.it/preprints/a194_paper.pdf

The mergers of galaxy clusters are the most energetic events in the universe after the Big Bang. With the increased availability of multi-object spectroscopy and X-ray data an ever increasing fraction of local clusters are recognised as exhibiting signs of recent or past merging events on various scales. Our goal is to probe how these mergers affect the evolution and content of their member galaxies. We specifically aim to answer the following questions: Is the quenching of star formation in merging clusters enhanced when compared with relaxed clusters? Is the quenching preceded by a (short lived) burst of star formation? We obtained optical spectroscopy of >400 galaxies in the field of the merging cluster Abell 520. We combine these observations with archival data to get a comprehensive picture of the state of star formation in the members of this merging cluster. Finally, we compare these observations with a control sample of 10 non-merging clusters at the same redshift from The Arizona Cluster Redshift Survey (ACReS). We split the member galaxies in passive, star forming or recently quenched depending on their spectra. The core of the merger shows a decreased fraction of star forming galaxies compared to clusters in the non-merging sample. This region, dominated by passive galaxies, is extended along the axis of the merger. We find evidence of rapid quenching of the galaxies during the core passage with no signs of a star burst on the time scales of the merger (~0.4Gyr). Additionally, we report the tentative discovery of an infalling group along the main filament feeding the merger, currently at ~2.5 Mpc from the merger centre. This group contains a high fraction of star forming galaxies as well as ~2/3 of all the recently quenched galaxies in our survey., 18 pages, 15 figures. Accepted for publication in A&A

We present new deep images of the Coma Cluster from the ESA Herschel Space Observatory at wavelengths of 70, 100 and 160 microns, covering an area of 1.75 x 1.0 square degrees encompassing the core and southwest infall region. Our data display an excess of sources at flux densities above 100 mJy compared to blank-field surveys, as expected. We use extensive optical spectroscopy of this region to identify cluster members and hence produce cluster luminosity functions in all three photometric bands. We compare our results to the local field galaxy luminosity function, and the luminosity functions from the Herschel Virgo Cluster Survey (HeViCS). We find consistency between the shapes of the Coma and field galaxy luminosity functions at all three wavelengths, however we do not find the same level of agreement with that of the Virgo Cluster., 8 pages, 5 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

We present the optical spectroscopy for the Blind Ultra Deep H I Environmental Survey (BUD-HIES). With the Westerbork Synthesis Radio Telescope, BUDHIES has detected H I in over 150 galaxies in and around two Abell clusters at z similar or equal to 0.2. With the aim of characterizing the environments of the H I-detected galaxies, we obtained multifibre spectroscopy with the William Herschel Telescope. In this paper, we describe the spectroscopic observations, report redshifts and EW[O II] measurements for similar to 600 galaxies, and perform an environmental analysis. In particular, we present cluster velocity dispersion measurements for five clusters and groups in the BUDHIES volume, as well as a detailed substructure analysis.

We present a reconstruction of the mass distribution of galaxy cluster Abell 1689 at z = 0.18 using detected strong lensing features from deep ACS observations and extensive ground based spectroscopy. Earlier analyses have reported up to 32 multiply imaged systems in this cluster, of which only 3 were spectroscopically confirmed. In this work, we present a parametric strong lensing mass reconstruction using 34 multiply imaged systems of which 24 have newly determined spectroscopic redshifts, which is a major step forward in building a robust mass model. In turn, the new spectroscopic data allows a more secure identification of multiply imaged systems. The resultant mass model enables us to reliably predict the redshifts of additional multiply imaged systems for which no spectra are currently available, and to use the location of these systems to further constrain the mass model. Using our strong lensing mass model, we predict on larger scale a shear signal which is consistent with that inferred from our large scale weak lensing analysis derived using CFH12K wide field images. Thanks to a new method for reliably selecting a well defined background lensed galaxy population, we resolve the discrepancy found between the NFW concentration parameters derived from earlier strong and weak lensing analysis. The derived parameters for the best fit NFW profile is found to be c(200) 7.6 +/- 1.6 and r(200) = 2.16 +/- 0.10 h(70)(-1) Mpc ( corresponding to a 3D mass equal to M(200) = [1.32 +/- 0.2] x 10(15) h(70) M circle dot). The large number of new constraints incorporated in this work makes Abell 1689 the most reliably reconstructed cluster to date. This well calibrated mass model, which we here make publicly available, will enable us to exploit Abell 1689 efficiently as a gravitational telescope, as well as to potentially constrain cosmology.

We have investigated the properties of the diffuse light in the Virgo Cluster core region, based on the detection of intracluster planetary nebulae (PNs) in four fields. We eliminate the bias from misclassified faint continuum objects, using improved Monte Carlo simulations, and the contaminations by high-redshift Ly alpha galaxies, using the Ly alpha luminosity function in blank fields. Recent spectroscopic observations confirm that our photometric PN samples are well understood. We find that the diffuse stellar population in the Virgo core region is inhomogeneous on scales of 30' - 90': there exist significant field-to-field variations in the number density of PNs and the inferred amount of intracluster light, with some fields empty, some fields dominated by extended Virgo galaxy halos, and some fields dominated by the true intracluster component. There is no clear trend with distance from M87. The mean surface luminosity density, its rms variation, and the mean surface brightness of diffuse light in our four fields are Sigma(B) = 2.7 x 10(6) L-B. arcmin(-2), rms = 2.1 x 10(6) L-B. arcmin(-2), and (mu) over bar (B) = 29.0 mag arcsec(-2), respectively. Our results indicate that the Virgo Cluster is a dynamically young environment and that the intracluster component is associated partially with local physical processes like galaxy interactions or harassment. We also argue, based on kinematic evidence, that the so-called over-luminous PNs in the halo of M84 are dynamically associated with this galaxy and must thus be brighter than, and part of a different stellar population from, the normal PN population in elliptical galaxies.

We have investigated the properties of the diffuse light in the Virgo cluster core region, based on the detection of intracluster planetary nebulae (PNe) in four fields. We eliminate the bias from misclassified faint continuum objects, using improved Monte Carlo simulations, and the contaminations by high redshift Ly$\alpha$ galaxies, using the Ly$\alpha$ luminosity function in blank fields. Recent spectroscopic observations confirm that our photometric PN samples are well-understood. We find that the diffuse stellar population in the Virgo core region is inhomogeneous on scales of 30'-90': there exist significant field-to-field variations in the number density of PNe and the inferred amount of intracluster light, with some empty fields, some fields dominated by extended Virgo galaxy halos, and some fields dominated by the true intracluster component. There is no clear trend with distance from M87. The mean surface luminosity density, its rms variation, and the mean surface brightness of diffuse light in our 4 fields are $\Sigma_B = 2.7 x 10^{6}$ L$_{B\odot}$ arcmin$^{-2}$, ${rms} = 2.1 \times 10^{6}$ L$_{B\odot}$ arcmin$^{-2}$, and $\bar{\mu}_{B}=29.0$ mag arcsec$^{-2}$ respectively. Our results indicate that the Virgo cluster is a dynamically young environment, and that the intracluster component is associated at least partially with local physical processes like galaxy interactions or harassment. We also argue, based on kinematic evidence, that the so-called 'over-luminous' PNe in the halo of M84 are dynamically associated with this galaxy, and must thus be brighter than and part of a different stellar population from the normal PN population in elliptical galaxies., Comment: 31 pages, 6 figure. In press on the Astronomical Journal

We have formed "composite spectra'' by combining the integrated-light spectra of individual galaxies in eight intermediate-redshift and 12 low-redshift clusters of galaxies. Because these composite spectra have much higher signal-to-noise ratios than individual galaxy spectra, they are particularly useful in quantifying general trends in star formation for galaxy populations in distant clusters, z > 0.3. By measuring diagnostic features that represent stellar populations of very different ages, a grand composite spectrum can reflect the fractions of those populations as accurately as if excellent spectral measurements were available for each galaxy. Such composite spectra can also be useful in the study of finer spectral signatures, for example, spectral indices that break the age-metallicity degeneracy, and the shape of the Hdelta absorption line as an indicator of the age and duration of an epoch of starbursting galaxies in a cluster. Measuring the equivalent widths of spectral features in composite spectra is especially well suited for comparing the cosmic variance of star formation in clusters at a given redshift or comparing clusters over a range of redshifts. When we do this we find that [O II] emission and especially Balmer absorption is strong in each of our intermediate-redshift clusters and completely separable from a sample of 12 present-epoch clusters, where these features are weak. Cluster-to-cluster variations at a given epoch seem to be smaller than the strong trend in redshift, which suggests that cosmic evolution is the major factor in the star formation histories of cluster galaxies. Specifically, we show by comparison with the Hdelta strengths of present-epoch populations of continuously star-forming galaxies that the higher redshift samples must contain a much higher fraction of starburst galaxies than are found today in any environment.

We present a deep multi-colour CCD mosaic of the Coma cluster (Abell 1656), covering 5.2 deg^2 in the B and r bands, and 1.3 deg^2 in the U band. This large, homogeneous data set provides a valuable low redshift comparison sample for studies of galaxies in distant clusters. In this paper we present our survey, and study the dependence of the galaxy luminosity function (LF) on passband and radial distance from the cluster centre. The U, B and r band LFs of the complete sample cannot be represented by single Schechter functions. For the central area, r, Comment: Accepted for publication in MNRAS

[Abridged] To effectively investigate galaxy formation and evolution, it is of paramount importance to exploit homogeneous data for large samples of galaxies in different environments. The WINGS (WIde-field Nearby Galaxy-cluster Survey) project aim is to evaluate physical properties of galaxies in a complete sample of low redshift clusters to be used as reference sample for evolutionary studies. The WINGS survey is still ongoing and the original dataset will soon be enlarged with new observations. This paper presents the entire collection of WINGS measurements obtained so far. We decided to make use of the Virtual Observatory (VO) tools to share the WINGS database (that will be regularly updated) with the community. In the database each object has one unique identification (WINGSID). Each subset of estimated properties is accessible using a simple cone search (including wide-field images). We provide the scientific community the entire set of wide-field images. Furthermore, the published database contains photometry of 759,024 objects and surface brightness analysis for 42,275 and 41,463 galaxies in the V and B band, respectively. The completeness depends on the image quality, and on the cluster redshift, reaching on average 90% at V, 11 pages, 3 Figures. Accepted for publication in A & A

This study is part of the FOssil Groups Origin (FOGO) project which aims at carrying out a systematic and multiwavelength study of a large sample of fossil systems. Here we focus on the relation between the optical luminosity (Lopt) and X-ray luminosity (Lx). Out of a sample of 28 candidate fossil systems, we consider a sample of 12 systems whose fossil classification has been confirmed by a companion study. They are compared with the complementary sample of 16 systems whose fossil nature is not confirmed and with a subsample of 102 galaxy systems from the RASS-SDSS galaxy cluster survey. Fossil and normal systems span the same redshift range 0, Comment: A&A, 12 pages, 4 figures, 3 tables, typos corr. and paper re-number

[Abridged] We investigate the frequency of the various spectral types as a function both of the clusters' properties and of the galaxies' characteristics. In this way, using the same classification criteria adopted for higher redshift studies, we can consistently compare the properties of the local cluster population to those of their more distant counterparts. We describe a method we have developed to automatically measure the equivalent width of spectral lines in a robust way even in spectra with a non optimal signal to noise. Like this, we can derive a spectral classification reflecting the stellar content, based on the presence and strength of the [OII] and Hdelta lines. We are able to measure 4381 of the ~6000 originally observed spectra, in the fields of 48 clusters, 2744 of which are spectroscopically confirmed cluster members. The spectral classification is then analyzed as a function of galaxies' luminosity, stellar mass, morphology, local density and host cluster's global properties, and compared to higher redshift samples (MORPHS and EDisCS). The vast majority of galaxies in the local clusters population are passive objects, being also the most luminous and massive. At a magnitude limit of Mv, Comment: 22 pages, 12 Figures. Accepted for publication in A&A. Table A.1 (catalog of equivalent widths measurements) available on-line or upon request

We present a spectroscopic survey of the rich X-ray-selected galaxy cluster CL 1358+6245 at z = 0.328. When our 173 new multislit spectra of cluster galaxies are combined with data from the literature, we produce a catalog of 232 cluster members in a region 10' x 11' (3.5 Mpc x 3.8 Mpc) surrounding the brightest cluster galaxy. These data are used to study the structure and dynamics of the cluster and to examine the radial and velocity distributions as a function of spectral type. We classify the spectral types of the cluster members according to the strengths of the Balmer absorption lines (H delta, H gamma, and H beta) and the [O II] 3727 Angstrom emission line.We derive a mean redshift of z = 0.3283 +/- 0.0003 and a velocity dispersion of 1027(-45)(+51) km s(-1) for the 232 cluster members. However, the cluster velocity distribution is non-Gaussian, and we identify at least two subgroups with 10-20 members and dispersions ofThe changing mix of galaxy spectral types as a function of local galaxy density (or distance from the cluster center) in CL 1358+62 is similar to what is observed in nearby rich clusters. The percentage of emission-line galaxies increases steadily with radius from 9% +/- 3% within a radius of r(p) Our high-S/N spectra of the "E + A" galaxies allow a detailed comparison with spectra of nearby merging and strongly interacting galaxy systems. We find that nearby mergers have stronger [O II] 3727 Angstrom emission ([O II] EW > 5 Angstrom) than that observed for our E + A galaxies. This implies either that the E + A galaxies in CL 1358 + 62 were not formed through major mergers, or that if they were formed via merging, their gas supply was quickly depleted, possibly by the intracluster medium.

Using traditional morphological classifications of galaxies in 10 intermediate-redshift (z similar to 0.5) clusters observed with WFPC2 on the Hubble Space Telescope, we derive relations between morphology and local galaxy density similar to that found by Dressier for low-redshift clusters. Taken collectively, the ''morphology-density'' relationship, T-Sigma, for these more distant, presumably younger clusters is qualitatively similar to that found for the local sample, but a detailed comparison shows two substantial differences: (1) For the clusters in our sample, the T-Sigma relation is strong in centrally concentrated ''regular'' clusters, those with a strong correlation of radius and surface density, but nearly absent for clusters that are less concentrated and irregular, in contrast to the situation for low-redshift clusters, where a strong relation has been found for both. (2) In every cluster the fraction of elliptical galaxies is as large or larger than in low-redshift clusters, but the SO fraction is 2-3 times smaller, with a proportional increase of the spiral fraction. Straightforward, though probably not unique, interpretations of these observations are (1) morphological segregation proceeds hierarchically, affecting richer, denser groups of galaxies earlier, and (2) the formation of elliptical galaxies predates the formation of rich clusters and occurs instead in the loose-group phase or even earlier, but SO's are generated in large numbers only after cluster virialization.

We present the optical spectroscopy for the Blind Ultra Deep H I Environmental Survey (BUD-HIES). With the Westerbork Synthesis Radio Telescope, BUDHIES has detected H I in over 150 galaxies in and around two Abell clusters at z similar or equal to 0.2. With the aim of characterizing the environments of the H I-detected galaxies, we obtained multifibre spectroscopy with the William Herschel Telescope. In this paper, we describe the spectroscopic observations, report redshifts and EW[O II] measurements for similar to 600 galaxies, and perform an environmental analysis. In particular, we present cluster velocity dispersion measurements for five clusters and groups in the BUDHIES volume, as well as a detailed substructure analysis.

The origins of S0 galaxies remain obscure, with various mechanisms proposed for their formation, likely depending on environment. These mechanisms would imprint different signatures in the galaxies' stellar kinematics out to large radii, offering a method for distinguishing between them. We aim to study a sample of six S0 galaxies from a range of environments, and use planetary nebulae (PNe) as tracers of their stellar populations out to very large radii, to determine their kinematics in order to understand their origins. Using a special-purpose instrument, the Planetary Nebula Spectrograph, we observe and extract PNe catalogues for these six systems*. We show that the PNe have the same spatial distribution as the starlight, that the numbers of them are consistent with what would be expected in a comparable old stellar population in elliptical galaxies, and that their kinematics join smoothly onto those derived at smaller radii from conventional spectroscopy. The high-quality kinematic observations presented here form an excellent set for studying the detailed kinematics of S0 galaxies, in order to unravel their formation histories. We find that PNe are good tracers of stellar kinematics in these systems. We show that the recovered kinematics are largely dominated by rotational motion, although with significant random velocities in most cases., Comment: 13, 8 figures, accepted in A&A

Central velocity dispersions, Mg-2 line indices and radial velocities for 220 E and SO galaxies are derived on the basis of intermediate resolution spectroscopy. Galaxies in the following clusters have been observed: Abell 194, Abell 539, Abell 3381, Abell 3574, S639, S753, Doradus, HydraI (Abell 1060) and Grm 15. For 151 of the galaxies, the velocity dispersion has not previously been measured. 134 of the Mg-2 determinations are for galaxies with no previous measurement. The spectra cover either 500 or 1000 Angstrom, centred on the magnesium triplet at 5177 Angstrom. The observations were obtained with the Boiler & Chivens spectrograph at the ESO 1.5-m telescope and with OPTOPUS, a multi-object fibre-fed B&C spectrograph, at the ESO 3.6-m telescope. The data are part of our ongoing study of the large-scale motions in the Universe and the physical background for the Fundamental Plane.The Fourier fitting method was used to derive the velocity dispersions and radial velocities. The velocity dispersions have been corrected for the effect of the size of the aperture. The correction was established on the basis of velocity dispersion profiles available in the literature. A comparison with results from Davies et al. shows that the derived central velocity dispersions have an rms error of 0.036 in log sigma. There is no offset relative to the velocity dispersions from Davies et al. The offset relative to data from Lucey & Carter is - 0.017 +/- 0.011 in log sigma, with our velocity dispersions being the smallest. The velocity dispersions derived from the B&C and the OPTOPUS observations, as well as the velocity dispersions published by Davies et al., Dressier, Lucey & Carter and Lucey et al., can be brought on a system consistent within 3 per cent.The Mg-2 line indices have been corrected for the size of the apertures, transformed to the Lick system, and corrected for the effect of the velocity dispersion. From comparison with data from Davies et al. and from Faber, we find that the rms error of Mg-2 is 0.013. Comparisons of the radial velocities with data from the literature show that our determinations are accurate to within approximate to 35 km s(-1). The accuracies reached for these observations are adequate for the study of the large-scale motions in the Universe and for investigations of the Fundamental Plane.

CCD surface photometry for 232 E and S0 galaxies is presented. The galaxies are observed in Gunn r and Johnson B, or Gunn r and g. For 48 of the galaxies surface photometry in Johnson U is also presented. Aperture magnitudes in Gunn v are derived for half of the galaxies. Galaxies in the following clusters have been observed: Abell 194, Abell 539, Abell 3381, Abell 3574, Abell S639, Abell S753, HydraI (Abell 1060), DC2345 - 28, Doradus and Grm15. The data are part of our ongoing study of the large-scale motions in the Universe and the physical background for the fundamental plane. We use a full model fitting technique for analysing the CCD images. This gives radial profiles of local surface brightness, colour, ellipticity and position angle. The residuals relative to the elliptical isophotes are described quantitatively by Fourier expansions. Effective radius, mean surface brightness and total magnitude are derived by fitting a de Vaucouleurs r(1/4) growth curve. We have derived a characteristic radius r(n) similar to the diameter D-n introduced by Dressier et al. The derivation of the effective parameters and of r(n) takes the seeing into account. We confirm the results by Saglia et al. that the effects of the seeing can be substantial. Seeing-corrected Values of the effective parameters and r(n) are also presented for 147 E and S0 galaxies in the Coma cluster. Colours, colour gradients and geometrical parameters are derived. The photometry is internally consistent within 0.016 mag. Comparison with the photoelectric aperture photometry from Burstein et al. shows a mean offset of 0.010 mag with an rms scatter of 0.034 mag. The global photometric parameters are compared with data from Faber et al., Lucey et al. and Lucey and Carter. These comparisons imply that the typical rms errors are as follows - log r(n): +/- 0.015; log r(e): +/-0.045; m(T): +/-0.09 mag; [mu](e): +/-0.16 mag. The rms error on the combination log r(e)- 0.35 [mu](e) which enters the fundamental plane is +/-0.020. Also, comparisons with data from Saglia et al. are presented. The accuracy of the absolute photometry, as well as the derived parameters, makes the data suitable for our investigations of the fundamental plane and of the large-scale motions in the Universe.

Velocity dispersion profiles and rotation curves have been determined for a sample of 13 brightest duster galaxies (BCGs) in order to study their internal stellar kinematics and investigate their relationship to ellipticals. We find that BCGs generally display velocity dispersion profiles with gradients similar to those found in normal bright ellipticals. A rising velocity dispersion profile is found for the BCG IC 1101, the dominant member of Abell 2029, confirming Dressier's (1979) result. No other rising velocity dispersion profiles are found in our sample suggesting that they are not a feature common to brightest duster galaxies. Significant rotation is found in only two of the galaxies, a result in agreement with previous studies showing the declining importance of rotation with increasing luminosity for elliptical galaxies. Our data suggest that environment plays a role in the kinematic characteristics of BCGs. We find a correlation between the rotation of BCGs and the velocity dispersion of their parent clusters in the sense that very slowly rotating galaxies (V-m/(sigma))(not asymptotic to) 650 km s(-1)) clusters. This relation between the internal stellar kinematics of BCGs and the cluster velocity dispersion is in the sense expected if ellipticals formed by merging. Brightest duster galaxy mass-to-light ratios derived from photometric and kinematic modeling are found to be similar to normal elliptical M/L values. For the galaxy NGC 4073, the dominant galaxy in the poor cluster MKW 4, we find that it contains a counterrotating stellar core suggestive of the occurrence of an accretion event(s).

We re-evaluate the experimental data concerning the large scale structure of the universe utilizing the theoretical methods of modern statistical mechanics. This allows us to test the implicit assumptions of analyticity and homogeneity present in the usual analysis. The results are quite surprising: the previous methods of analysis are mathematically inconsistent for all the cases that can be explicitly tested. In view of the untested homogeneity assumption, these methods give rise to a finite correlation length even in systems that do not possess one (i.e. those with long range power law correlations). In particular, we demonstrate that the famous galaxy correlation length r0 almost-equal-to 5h-1 Mpc is a spurious result due to these inconsistencies. In fact it is related to the cut-off due to the finiteness of the sample and not to the correlation properties of galaxies. We can therefore predict that the value of r0 will increase with sample depth when deeper complete catalogs are available. The reanalysis of galaxy and cluster catalogs without any assumption shows long range (fractal) correlations up to the sample limits. This explains the previous contradiction between the correlation analysis and the observation of large scale structures like voids and superclusters. The correlation length, in fact, cannot be much smaller than the size of the largest structures one can observe. We also consider the angular projection of systems with long range correlations and explain why the angular distributions appear to be more homogeneous than the three dimensional ones. These studies are then generalized by an analysis of the whole distribution of visible matter (by including an estimate of the galaxy masses) which shows well defined multifractal properties. This allows one to clarify various other problems such as the so-called "luminosity segregation" phenomenon and the "richness-clustering" relation. In addition the multifractal behavior implies that the upper cut-off of the luminosity function scales with the size of the sample with a characteristic exponent which we determine. This fact has direct implications for galaxy number counts and for several other problems. One may even conjecture in this respect, that quasars may actually represent the continuation of this scaling behavior to much larger scales. In summary a new picture appears which is fundamentally different from the usual one but actually much simpler: the distribution of visible matter in the universe appears to be fractal and multifractal up to the present observational limits (200 Mpc; about one twentieth of the Hubble radius of the entire universe) without any evidence for homogenization. This implies that the nature of the distribution is strongly non-analytic and no simple average density can be defined. These results have profound consequences for our knowledge of the properties of the universe as well as for the theoretical framework that one should use to describe it.

We present the rest-frame optical luminosity function (LF) of red sequence galaxies in 16 clusters at 0.4, Comment: Accepted for publication in the Astrophysical Journal. 36 pages, 16 figures, 10 tables

We have compiled a sample of early-type cluster galaxies from 0 < z < 1.3 and measured the evolution of their ellipticity distributions. Our sample contains 487 galaxies in 17 z>0.3 clusters with high quality space-based imaging and a comparable sample of 210 galaxies in 10 clusters at z M_B > -21, after correcting for luminosity evolution. Our ellipticity measurements are made in a consistent manner over our whole sample. We perform extensive simulations to quantify the systematic and statistical errors, and find that it is crucial to use PSF-corrected model fits. We find that neither the median ellipticity, nor the shape of the ellipticity distribution of cluster early-type galaxies evolves with redshift from z ~ 0 to z > 1. These results are strongly suggestive of an unchanging overall bulge-to-disk ratio distribution for cluster early-type galaxies over the last ~8Gyr. This result contrasts with that from visual classifications which show that the fraction of morphologically-selected disk-dominated early-type galaxies, or S0s, is significantly lower at z>0.4 than at z~0. Taking the ellipticity measurements and assuming, as in all previous studies, that the intrinsic ellipticity distribution of both elliptical and S0 galaxies remains constant, then we conclude from the lack of evolution in the observed early-type ellipticity distribution that the relative fractions of ellipticals and S0s do not evolve from z~1 to z=0 for a red-sequence selected samples of galaxies in the cores of clusters of galaxies., 21 pages, 15 color figures, revised to match final ApJ version. Corrected discussion of Andreon et al 1996 from previous version

We present optical and infrared photometry (BV RI, J H K) and spectra of galaxies in 6 medium redshift clusters covering the redshift range 0.19 less-than-or-equal-to z less-than-or-equal-to 0.4. The array photometry is used to note the radial distribution of the cluster galaxies with optical and infrared colours. By bisecting the galaxy population into red and blue halves, the tendency of the bluer galaxies to define rims or shells around the cores of the more distant clusters is noted, and its implications for delayed star formation briefly discussed. The optical photometry is also used to confirm flux calibrations of the long slit and multiple object spectra (12 angstrom resolution) which have been taken for a sample of central elliptical galaxies in each cluster. The infrared photometry is used to extend the broad-band flux levels for these spectra. The de-redshifted spectra are synthesised in paper III in terms of the isochrone models presented in Paper I, to derive an averaged history of star formation for these clusters as a function of redshift.

AIMS. We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. METHODS. We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the clusters using the Dressler-Shectman test. RESULTS. The method of subtracting the sky prior to any rebinning/interpolation of the data delivers photon-noise-limited results, whereas the traditional method of subtracting the sky after the data have been rebinned/interpolated results in substantially larger noise for spectra from tilted slits. Redshifts for individual galaxies are presented and redshifts and velocity dispersions are presented for 21 galaxy clusters. For the 9 clusters with at least 20 spectroscopically confirmed members, we present the statistical significance of the presence of substructure obtained from the Dressler-Shectman test, and substructure is detected in two of the clusters. CONCLUSIONS. Together with data from our previous paper, spectroscopy and spectroscopic velocity dispersions are now available for 26 EDisCS clusters with redshifts in the range 0.40-0.96 and velocity dispersions in the range 166-1080 km/s., Comment: 31 pages, 23 figures, accepted for publication in A&A

Theories of structure formation in a cold dark matter dominated Universe predict that massive clusters of galaxies assemble from the hierarchical merging of lower mass subhalos. Exploiting strong and weak gravitational lensing signals inferred from panoramic HST imaging data, we present a high resolution reconstruction of the mass distribution in the massive, lensing cluster Cl0024+16. Applying galaxy-galaxy lensing techniques we track the fate of dark matter subhalos as a function of projected cluster-centric radius out to 5 Mpc, well beyond the virial radius. We report the first detection of the statistical lensing signal of dark matter subhalos associated with late-type galaxies in clusters. The mass of a typical dark matter subhalo that hosts an L* galaxy increases with projected cluster-centric radius in line with expectations from the tidal stripping hypothesis. Early-type galaxies appear to be hosted on average in more massive dark matter subhalos compared to late-type galaxies. We interpret our findings as evidence for the active assembly of mass via tidal stripping in galaxy clusters. The mass function of dark matter subhalos as a function of projected cluster-centric radius, is compared with an equivalent mass function derived from clusters in the Millenium Run simulation populated with galaxies using semi-analytic models. The shape of the lensing determined mass functions are in very good agreement with the subhalo mass functions derived from the Millenium Run simulation. However, simulated subhalos appear to be more efficiently stripped than lensing observations suggest. (Abridged), 35 pages, 7 figures, revised version, accepted by ApJ

We present a reconstruction of the mass distribution of galaxy cluster Abell 1689 at z = 0.18 using detected strong lensing features from deep HST/ACS observations and extensive ground based spectroscopy. Earlier analyses have reported up to 32 multiply imaged systems in this cluster, of which only 3 were spectroscopically confirmed. In this work, we present a parametric strong lensing mass reconstruction using 24 multiply imaged systems with newly determined spectroscopic redshifts, which is a major step forward in building a robust mass model. In turn, the new spectroscopic data allows a more secure identification of multiply imaged systems. The resultant mass model enables us to reliably predict the redshifts of additional multiply imaged systems for which no spectra are currently available, and to use the location of these systems to further constrain the mass model. In particular, we have detected 5 strong galaxy-galaxy lensing systems just outside the Einstein ring region, further constraining the mass profile. Our strong lensing mass model is consistent with that inferred from our large scale weak lensing analysis derived using CFH12k wide field images. Thanks to a new method for reliably selecting a well defined background lensed galaxy population, we resolve the discrepancy found between the strong and weak lensing mass models reported in earlier work. [ABRIDGED], ApJ in press, 668, 643. Final article with figures and online data available at http://archive.dark-cosmology.dk/

In this paper we serendipitously identify X-ray cluster candidates using XMM-Newton archival observations complemented by 5-band optical photometric follow-up observations (r~23 mag) as part of the X-ray Identification (XID) programme. Our sample covers an area of ~2.1 sq. deg (15 XMM-Newton fields) and comprises a total of 21 (19 serendipitous + 2 target) extended X-ray sources to the limit f(0.5-2keV) ~ 6x10^{-15} cgs with a high probability (> 99.9%) of being extended on the XMM-Newton images. Of the 21 cluster candidates 7 are spectroscopically confirmed in the literature. Exploiting the optical data available for these fields we discover that 68% of the X-ray cluster candidates are associated with optical galaxy overdensities. We also attempt to constrain the redshifts of our cluster candidates using photometric methods. We thus construct the photometric redshift distribution of galaxies in the vicinity of each X-ray selected cluster candidate and search for statistically significant redshift peaks against that of the background distribution of field galaxies. Comparison of the photometric with spectroscopic redshift estimates for the confirmed clusters suggest that our simple method is robust out to z~0.5. For clusters at higher z, deeper optical data are required to estimate reliable photometric redshifts. Finally, using the sample of the 19 serendipitous X-ray selected cluster candidates we estimate their surface density down to f(0.5-2keV) ~ 6x10^{-15} cgs and find it to be in fair agreement with previous and recent studies., Submitted to the MNRAS, 8 pages

We have formed ``composite spectra'' by combining the integrated-light spectra of individual galaxies in 8 intermediate-redshift and 12 low-redshift clusters of galaxies. Because these composite spectra have much higher signal-to-noise ratios than individual galaxy spectra, they are particularly useful in quantifying general trends in star formation for galaxy populations in distant clusters, z > 0.3. By measuring diagnostic features that represent stellar populations of very different ages, a grand-composite spectrum can reflect the fractions of those populations as accurately as if excellent spectral measurements were available for each galaxy. Measuring the equivalent widths of spectral features in composite spectra is especially well-suited for comparing cosmic variance of star formation in clusters at a given redshift, or comparing clusters over a range of redshifts. When we do this we find that [O II] emission and especially Balmer absorption is strong in each of our intermediate-redshift clusters, and completely separable from a sample of 12 present-epoch clusters, where these features are weak. Specifically, we show by comparing to the H-delta strengths of present-epoch populations of continuously star-forming galaxies that the higher-redshift samples must contain a much higher fraction of starburst galaxies than are found today in any environment., 30 pages, 8 figures. Accepted for publication in ApJ (20 November 2004, vol 616 issue)

The density and velocity fields as extracted from the Abell/ACO clusters are compared to the corresponding fields recovered by the POTENT method from the Mark~III peculiar velocities of galaxies. In order to minimize non-linear effects and to deal with ill-sampled regions we smooth both fields using a Gaussian window with radii ranging between $12 - 20\hmpc$. The density and velocity fields within $70\hmpc$ exhibit similarities, qualitatively consistent with gravitational instability theory and a linear biasing relation between clusters and mass. The random and systematic errors are evaluated with the help of mock catalogs. Quantitative comparisons within a volume containing $\sim\!12$ independent samples yield $\betac\equiv\Omega^{0.6}/b_c=0.22\pm0.08$, where $b_c$ is the cluster biasing parameter at $15\hmpc$. If $b_c \sim 4.5$, as indicated by the cluster correlation function, our result is consistent with $\Omega \sim 1$., Comment: 18 pages, latex, 2 ps figures 6 gif figures. Accepted for pubblications in MNRAS

We present a spectroscopic survey of the rich, X-ray selected, galaxy cluster CL 1358+6245 at z=0.328. When our 173 new multi-slit spectra of cluster galaxies are combined with data from the literature, we produce a catalog of 232 cluster members in a region 10'x11' (3.5 Mpc x 3.8 Mpc) surrounding the brightest cluster galaxy. These data are used to study the structure and dynamics of the cluster and to examine the radial and velocity distributions as a function of spectral type. We classify the spectral types of the cluster members according to the strengths of the Balmer absorption lines (Hdelta, Hgamma, and Hbeta) and the [OII] 3727 Ang emission line., 29 pages, 14 figures, uses aas2pp4, Accepted for publication in ApJ

Some years ago we proposed a new approach to the analysis of galaxy and cluster correlations based on the concepts and methods of modern statistical Physics. This led to the surprising result that galaxy correlations are fractal and not homogeneous up to the limits of the available catalogs. The usual statistical methods, which are based on the assumption of homogeneity, are therefore inconsistent for all the length scales probed so far, and a new, more general, conceptual framework is necessary to identifythe real physical properties of these structures. In the last few years the 3-d catalogs have been significatively improved and we have extended our methods to the analysis of number counts and angular catalogs. This has led to a complete analysis of all the available data that we present in this review. The result is that galaxy structures are highly irregular and self-similar: all the available data are consistent with each other and show fractal correlations (with dimension $D \simeq 2$) up to the deepest scales probed so far ($1000 \hmp$) and even more as indicated from the new interpretation of the number counts. The evidence for scale-invariance of galaxy clustering is very strong up to $150 \hmp$ due to the statistical robustness of the data but becomes progressively weaker (statistically) at larger distances due to the limited data. In These facts lead to fascinating conceptual implications about our knowledge of the universe and to a new scenario for the theoretical challenge in this field., Comment: Latex file 165 pages, 106 postscript figures. This paper is also available at http://www.phys.uniroma1.it/DOCS/PIL/pil.html To appear in Physics Report (Dec. 1997)

Using traditional morphological classifications of galaxies in 10 intermediate-redshift (z similar to 0.5) clusters observed with WFPC2 on the Hubble Space Telescope, we derive relations between morphology and local galaxy density similar to that found by Dressier for low-redshift clusters. Taken collectively, the ''morphology-density'' relationship, T-Sigma, for these more distant, presumably younger clusters is qualitatively similar to that found for the local sample, but a detailed comparison shows two substantial differences: (1) For the clusters in our sample, the T-Sigma relation is strong in centrally concentrated ''regular'' clusters, those with a strong correlation of radius and surface density, but nearly absent for clusters that are less concentrated and irregular, in contrast to the situation for low-redshift clusters, where a strong relation has been found for both. (2) In every cluster the fraction of elliptical galaxies is as large or larger than in low-redshift clusters, but the SO fraction is 2-3 times smaller, with a proportional increase of the spiral fraction. Straightforward, though probably not unique, interpretations of these observations are (1) morphological segregation proceeds hierarchically, affecting richer, denser groups of galaxies earlier, and (2) the formation of elliptical galaxies predates the formation of rich clusters and occurs instead in the loose-group phase or even earlier, but SO's are generated in large numbers only after cluster virialization.

We present a combined optical and X-ray analysis of the rich cluster Abell 1882 with the aim of identifying merging substructure and understanding the recent assembly history of this system. Our optical data consist of spectra drawn from the Galaxy and Mass Assembly (GAMA) survey, which lends itself to this kind of detailed study thanks to its depth and high spectroscopic completeness. We use 283 spectroscopically confirmed cluster members to detect and characterize substructure. We complement the optical data with X-ray data taken with both Chandra and XMM. Our analysis reveals that A1882 harbors two main components, A1882A and A1882B, which have a projected separation of 2Mpc and a line of sight velocity difference of v_{los}=-428km/s. The primary system, A1882A, has velocity dispersion sigma_v=500km/s and Chandra (XMM) temperature kT=3.57keV (3.31keV) while the secondary, A1882B, has sigma_v=457km/s and Chandra (XMM) temperature kT=2.39keV (2.12keV). The optical and X-ray estimates for the masses of the two systems are consistent within the uncertainties and indicate that there is twice as much mass in A1882A (M_{500}=1.5-1.9x10^{14}Msolar) when compared with A1882B (M_{500}=0.8-1.0x10^{14}Msolar). We interpret the A1882A/A1882B system as being observed prior to a core passage. Supporting this interpretation is the large projected separation of A1882A and A1882B and the dearth of evidence for a recent (, 20 pages, 10 figures, 6 tables. Accepted for publication in ApJ

Central velocity dispersions, Mg-2 line indices and radial velocities for 220 E and SO galaxies are derived on the basis of intermediate resolution spectroscopy. Galaxies in the following clusters have been observed: Abell 194, Abell 539, Abell 3381, Abell 3574, S639, S753, Doradus, HydraI (Abell 1060) and Grm 15. For 151 of the galaxies, the velocity dispersion has not previously been measured. 134 of the Mg-2 determinations are for galaxies with no previous measurement. The spectra cover either 500 or 1000 Angstrom, centred on the magnesium triplet at 5177 Angstrom. The observations were obtained with the Boiler & Chivens spectrograph at the ESO 1.5-m telescope and with OPTOPUS, a multi-object fibre-fed B&C spectrograph, at the ESO 3.6-m telescope. The data are part of our ongoing study of the large-scale motions in the Universe and the physical background for the Fundamental Plane. The Fourier fitting method was used to derive the velocity dispersions and radial velocities. The velocity dispersions have been corrected for the effect of the size of the aperture. The correction was established on the basis of velocity dispersion profiles available in the literature. A comparison with results from Davies et al. shows that the derived central velocity dispersions have an rms error of 0.036 in log sigma. There is no offset relative to the velocity dispersions from Davies et al. The offset relative to data from Lucey & Carter is - 0.017 +/- 0.011 in log sigma, with our velocity dispersions being the smallest. The velocity dispersions derived from the B&C and the OPTOPUS observations, as well as the velocity dispersions published by Davies et al., Dressier, Lucey & Carter and Lucey et al., can be brought on a system consistent within 3 per cent. The Mg-2 line indices have been corrected for the size of the apertures, transformed to the Lick system, and corrected for the effect of the velocity dispersion. From comparison with data from Davies et al. and from Faber, we find that the rms error of Mg-2 is 0.013. Comparisons of the radial velocities with data from the literature show that our determinations are accurate to within approximate to 35 km s(-1). The accuracies reached for these observations are adequate for the study of the large-scale motions in the Universe and for investigations of the Fundamental Plane.

CCD surface photometry for 232 E and S0 galaxies is presented. The galaxies are observed in Gunn r and Johnson B, or Gunn r and g. For 48 of the galaxies surface photometry in Johnson U is also presented. Aperture magnitudes in Gunn v are derived for half of the galaxies. Galaxies in the following clusters have been observed: Abell 194, Abell 539, Abell 3381, Abell 3574, Abell S639, Abell S753, HydraI (Abell 1060), DC2345 - 28, Doradus and Grm15. The data are part of our ongoing study of the large-scale motions in the Universe and the physical background for the fundamental plane. We use a full model fitting technique for analysing the CCD images. This gives radial profiles of local surface brightness, colour, ellipticity and position angle. The residuals relative to the elliptical isophotes are described quantitatively by Fourier expansions. Effective radius, mean surface brightness and total magnitude are derived by fitting a de Vaucouleurs r(1/4) growth curve. We have derived a characteristic radius r(n) similar to the diameter D-n introduced by Dressier et al. The derivation of the effective parameters and of r(n) takes the seeing into account. We confirm the results by Saglia et al. that the effects of the seeing can be substantial. Seeing-corrected Values of the effective parameters and r(n) are also presented for 147 E and S0 galaxies in the Coma cluster. Colours, colour gradients and geometrical parameters are derived. The photometry is internally consistent within 0.016 mag. Comparison with the photoelectric aperture photometry from Burstein et al. shows a mean offset of 0.010 mag with an rms scatter of 0.034 mag. The global photometric parameters are compared with data from Faber et al., Lucey et al. and Lucey and Carter. These comparisons imply that the typical rms errors are as follows - log r(n): +/- 0.015; log r(e): +/-0.045; m(T): +/-0.09 mag; [mu](e): +/-0.16 mag. The rms error on the combination log r(e)- 0.35 [mu](e) which enters the fundamental plane is +/-0.020. Also, comparisons with data from Saglia et al. are presented. The accuracy of the absolute photometry, as well as the derived parameters, makes the data suitable for our investigations of the fundamental plane and of the large-scale motions in the Universe.

We present optical and infrared photometry (BV RI, J H K) and spectra of galaxies in 6 medium redshift clusters covering the redshift range 0.19 less-than-or-equal-to z less-than-or-equal-to 0.4. The array photometry is used to note the radial distribution of the cluster galaxies with optical and infrared colours. By bisecting the galaxy population into red and blue halves, the tendency of the bluer galaxies to define rims or shells around the cores of the more distant clusters is noted, and its implications for delayed star formation briefly discussed. The optical photometry is also used to confirm flux calibrations of the long slit and multiple object spectra (12 angstrom resolution) which have been taken for a sample of central elliptical galaxies in each cluster. The infrared photometry is used to extend the broad-band flux levels for these spectra. The de-redshifted spectra are synthesised in paper III in terms of the isochrone models presented in Paper I, to derive an averaged history of star formation for these clusters as a function of redshift.

We present optical and infrared photometry (BV RI, J H K) and spectra of galaxies in 6 medium redshift clusters covering the redshift range 0.19 less-than-or-equal-to z less-than-or-equal-to 0.4. The array photometry is used to note the radial distribution of the cluster galaxies with optical and infrared colours. By bisecting the galaxy population into red and blue halves, the tendency of the bluer galaxies to define rims or shells around the cores of the more distant clusters is noted, and its implications for delayed star formation briefly discussed. The optical photometry is also used to confirm flux calibrations of the long slit and multiple object spectra (12 angstrom resolution) which have been taken for a sample of central elliptical galaxies in each cluster. The infrared photometry is used to extend the broad-band flux levels for these spectra. The de-redshifted spectra are synthesised in paper III in terms of the isochrone models presented in Paper I, to derive an averaged history of star formation for these clusters as a function of redshift.

SPIDERS (The SPectroscopic IDentification of eROSITA Sources) is a program dedicated to the homogeneous and complete spectroscopic follow-up of X-ray AGN and galaxy clusters over a large area ($\sim$7500 deg$^2$) of the extragalactic sky. SPIDERS is part of the SDSS-IV project, together with the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) and the Time-Domain Spectroscopic Survey (TDSS). This paper describes the largest project within SPIDERS before the launch of eROSITA: an optical spectroscopic survey of X-ray selected, massive ($\sim 10^{14}$ to $10^{15}~M_{\odot}$) galaxy clusters discovered in ROSAT and XMM-Newton imaging. The immediate aim is to determine precise ($\Delta_z \sim 0.001$) redshifts for 4,000-5,000 of these systems out to $z \sim 0.6$. The scientific goal of the program is precision cosmology, using clusters as probes of large-scale structure in the expanding Universe. We present the cluster samples, target selection algorithms and observation strategies. We demonstrate the efficiency of selecting targets using a combination of SDSS imaging data, a robust red-sequence finder and a dedicated prioritization scheme. We describe a set of algorithms and work-flow developed to collate spectra and assign cluster membership, and to deliver catalogues of spectroscopically confirmed clusters. We discuss the relevance of line-of-sight velocity dispersion estimators for the richer systems. We illustrate our techniques by constructing a catalogue of 230 spectroscopically validated clusters ($0.031 < z < 0.658$), found in pilot observations. We discuss two potential science applications of the SPIDERS sample: the study of the X-ray luminosity-velocity dispersion ($L_X-\sigma$) relation and the building of stacked phase-space diagrams., Comment: 27 pages, 31 figures, 9 tables. Tables in electronic format are available from http://www.sdss.org. Submitted to MNRAS