Search

We combine observations from ALMA, ATCA, MUSE, andHerschel to study gas-to-dust ratios in 15 Fornax cluster galaxies detected in the FIR/sub-mm by Herschel and observed by ALMA as part of the ALMA Fornax Cluster Survey (AlFoCS). The sample spans a stellar mass range of 8.3 $\leq$ log (M$_*$ / M$_\odot$) $\leq$ 11.16, and a variety of morphological types. We use gas-phase metallicities derived from MUSE observations (from the Fornax3D survey) to study these ratios as a function of metallicity, and to study dust-to-metal ratios, in a sub-sample of nine galaxies. We find that gas-to-dust ratios in Fornax galaxies are systematically lower than those in field galaxies at fixed stellar mass/metallicity. This implies that a relatively large fraction of the metals in these Fornax systems is locked up in dust, which is possibly due to altered chemical evolution as a result of the dense environment. The low ratios are not only driven by HI deficiencies, but H$_2$-to-dust ratios are also significantly decreased. This is different in the Virgo cluster, where low gas-to-dust ratios inside the virial radius are driven by low HI-to-dust ratios, while H$_2$-to-dust ratios are increased. Resolved observations of NGC1436 show a radial increase in H$_2$-to-dust ratio, and show that low ratios are present throughout the disc. We propose various explanations for the low H$_2$-to-dust ratios in the Fornax cluster, including the more efficient stripping of H$_2$ compared to dust, more efficient enrichment of dust in the star formation process, and altered ISM physics in the cluster environment., Accepted for publication in MNRAS. 21 pages, 12 figures, and 3 tables

As part of the VESTIGE survey, a blind narrow-band Ha+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the CFHT, we discovered 8 massive lenticular galaxies with prominent ionised gas emission features in their inner (few kpc) regions. These features are either ionised gas filaments similar to those observed in cooling flows (2 gal), or thin discs with sizes 0.7, Comment: Accepted for publication on A&A

Using the VESTIGE survey, a deep narrow-band H$\alpha$ imaging survey of the Virgo cluster carried on at the CFHT with MegaCam, we discovered a long diffuse tail of ionised gas in the edge-on late-type galaxy NGC 4330. This peculiar feature witnesses an ongoing ram pressure stripping (RPS) event able to remove the gas in the outer disc region. Tuned hydrodynamic simulations suggest that the RPS event is occurring almost face-on, making NGC 4330 the ideal candidate to study the effects of the perturbation in the direction perpendicular to the disc plane. We present here two new independent sets of Fabry-Perot observations (R$\simeq$10000) in order to understand the effects of the RPS process on the ionised gas kinematics. Despite their limited sensitivity to the diffuse gas emission, the data allowed us to measure the velocity and the velocity dispersion fields over the galaxy disc and in several features at the edges or outside the stellar disc formed after the RPS event. We have constructed the position-velocity diagrams and the rotation curves of the galaxy using three different techniques. The data show, consistent with the hydrodynamic simulations, that the galaxy has an inner solid-body rotation up to $\sim$2.4 kpc, with non-circular streaming motions outwards the disc and in the several external features formed during the interaction of the galaxy with the surrounding intracluster medium. The data also indicate a decrease of the rotational velocity of the gas with increasing distance from the galaxy disc along the tails, suggesting a gradual but not linear loss of angular momentum in the stripped gas. Consistent with a RPS scenario, the $i$-band image shows a boxy shape at the southwest edge of the disc, where the stellar orbits might have been perturbed by the modification of the gravitational potential well of the galaxy due to the displacement of the gas in the $z$-direction., Comment: Accepted for publication on A&A

Low-surface-brightness galaxies (LSBs) contribute to a significant fraction of all the galaxies in the Universe. Ultra-diffuse galaxies (UDGs) form a subclass of LSBs that has attracted a lot of attention in recent years (although its definition may vary between studies). Although UDGs are found in large numbers in galaxy clusters, groups, and in the field, their formation and evolution are still very much debated. Using a comprehensive set of multiwavelength data from the NGVS (optical), VESTIGE (H$\alpha$ narrowband), and GUViCS (UV) surveys, we studied a sample of 64 diffuse galaxies and UDGs in the Virgo cluster to investigate their formation history. We analyzed the photometric colors and surface-brightness profiles of these galaxies and then compared them to models of galaxy evolution, including ram-pressure stripping (RPS) events to infer any possible strong interactions with the hot cluster gas in the past. While our sample consists mainly of red LSBs, which is typical in cluster environments, we found evidence of a color variation with the cluster-centric distance. Blue, HI-bearing, star-forming diffuse galaxies are found at larger distances from the cluster center than the rest of the sample. The comparison of our models with multifrequency observations suggests that most of the galaxies of the sample might have undergone a strong RPS event in their lifetime, on average 1.6 Gyr ago (with a large dispersion, and RPS still ongoing for some of them). This process resulted in the transformation of initially gas-rich diffuse blue galaxies into gas-poor and red ones that form the dominant population now, the more extreme UDGs having undergone the process in a more distant past on average. The RPS in dense environments could be one of the major mechanisms for the formation of the large number of quiescent UDGs we observe in galaxy clusters., Comment: 57 pages, 14 Figures, accepted for publication in A&A

We have observed the giant elliptical galaxy M87 during the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Halpha+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada French Hawaii Telescope (CFHT). The deep narrow-band image confirmed the presence of a filament of ionised gas extending up to ~ 3 kpc in the north-western direction and ~ 8 kpc to the south-east, with a couple of plumes of ionised gas, the weakest of which, at ~ 18 kpc from the nucleus, was previously unknown. The analysis of deep optical images taken from the NGVS survey confirms that this gas filament is associated with dust seen in absorption which is now detected up to ~ 2.4 kpc from the nucleus. We have also analysed the physical and kinematical properties of the ionised gas filament using deep IFU MUSE data covering the central 4.8 x 4.8 kpc^2 of the galaxy. The spectroscopic data confirms a perturbed kinematics of the ionised gas, with differences in velocity of ~ 700-800 km s^-1 on scales of < 1 kpc. The analysis of 2D diagnostic diagrams and the observed relationship between the shock-sensitive [OI]/Halpha line ratio and the velocity dispersion of the gas suggest that the gas is shock-ionised., Accepted for publication to Astronomy & Astrophysics

We study the IB(s)m galaxy IC 3476 observed in the context of the Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE), a blind narrow-band H +[NII] imaging survey of the Virgo cluster carried out with MegaCam at the CFHT. The deep narrowband image reveals a very pertubed ionised gas distribution that is characterised by a prominent banana-shaped structure in the front of the galaxy formed of giant HII regions crossing the stellar disc. Star-forming structures, at 8 kpc from the edges of the stellar disc, are also detected in a deep far-ultraviolet ASTROSAT/UVIT image. This particular morphology indicates that the galaxy is undergoing an almost edge-on ram pressure stripping event. The same H +[NII] image also shows that the star formation activity is totally quenched in the leading edge of the disc, where the gas has been removed during the interaction with the surrounding medium. The spectral energy distribution fitting analysis of the multi-frequency data indicates that this quenching episode is very recent ( 50 Myr), and roughly corresponds to an increase of the star formation activity by a factor of 161% in the inner regions with respect to that expected for secular evolution. The analysis of these data, whose angular resolution enables the study of the induced e ects of the perturbation down to the scale of individual HII regions (req ' 40 pc), also suggests that the increase of star formation activity is due to the compression of the gas along the stellar disc of the galaxy, which is able to increase its mean electron density and boost the star formation process producing bright HII regions with luminosities up to L(H ) ' 1038 erg s-1. The combined analysis of the VESTIGE data with deep IFU spectroscopy gathered with MUSE and with high spectral resolution Fabry Perot data also indicates that the hydrodynamic interaction has deeply perturbed the velocity field of the ionised gas component while leaving that of the stellar disc una ected. The comparison of the data with tuned high-resolution hydrodynamic simulations accounting for the di erent gas phases (atomic, molecular, ionised) consistently indicates that the perturbing event is very recent (50–150 Myr), once again confirming that ram pressure stripping is a violent phenomenon that is able to perturb the evolution of galaxies in rich environments on short timescales., "Programme National de Cosmologie and Galaxies" (PNCG) - CNRS/INSU-IN2P3-INP, Centre National D'etudes Spatiales, French Atomic Energy Commission, National Aeronautics & Space Administration (NASA), BEIS capital funding via STFC ST/K00042X/1 ST/P002293/1 ST/R002371/1 ST/S002502/1, Durham University, UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) ST/R000832/1, European Research Council (ERC) European Commission 740120, Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT 1170618, European Commission 839090, Spanish grant within the European Funds for Regional Development (FEDER) PGC2018-095317-B-C21, Academy of Finland European Commission 324504 328898, Fundacao de Amparo a Pesquisa do Estado da Bahia (FAPESB) PIE 0013/2016

著者人数: 12名, Accepted: 2015-10-08, 資料番号: SA1150215000

We have observed the late-type peculiar galaxy NGC 4424 during VESTIGE, a blind narrow-band Halpha[NII] imaging survey of the Virgo cluster carried out with MegaCam at the CFHT. The presence of a 110 kpc long HI tail in the S direction indicates that this galaxy is undergoing a ram pressure stripping event. The deep narrow-band image revealed the presence of a low surface brightness ionised gas tail ~10 kpc long extending from the centre of the galaxy to the NW direction, in the direction opposite to the HI tail. Chandra and XMM X-rays data do not show any compact source in the nucleus nor the presence of an extended tail of hot gas, while MUSE spectroscopy indicates that the gas is photo-ionised in the inner regions and shock-ionised in the outer parts. IFU spectroscopy confirms that the ionised gas is kinematically decoupled from the stellar component and indicates the presence of two kinematically distinct structures in the stellar disc. The analysis of the SED of the galaxy indicates that the activity of star formation has been totally quenched in the outer disc ~ 250-280 Myr ago, while only reduced by ~80% in the central regions. All this observational evidence suggests that NGC 4424 is the remnant of an unequal-mass merger occurred, Accepted for publication on Astronomy & Astrophysics

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band H$\alpha$+[NII] imaging survey carried out with MegaCam at the CFHT. During pilot observations we have observed NGC 4330, an intermediate mass, edge-on star forming spiral currently falling into the core of the Virgo cluster. New deep observations revealed a low surface brightness 10 kpc tail exhibiting a peculiar filamentary structure. The filaments are remarkably parallel one another and clearly indicate the direction of motion of the galaxy in the Virgo potential. Motivated by the detection of these features, indicating ongoing gas stripping, we collected literature photometry in 15 bands from the far-UV to the far-IR and deep optical long slit spectroscopy using the FORS2 instrument at the ESO Very Large Telescope. Using a newly developed Monte Carlo code that jointly fits spectroscopy and photometry, we reconstructed the star formation histories in apertures along the major axis of the galaxy. Our results have been validated against the output of CIGALE, a fitting code which has been previously used for similar studies. We found a clear outside-in gradient with radius of the time when the quenching event started: the outermost radii have been stripped 500 Myr ago, while the stripping has reached the inner 5 kpc from the center in the last 100 Myr. Regions at even smaller radii are currently still forming stars fueled by the presence of HI and H2 gas. When compared to statistical studies of the quenching timescales in the local Universe we find that ram pressure stripping of the cold gas is an effective mechanism to reduce the transformation times for galaxies falling into massive clusters. Future systematic studies of all the active galaxies observed by VESTIGE in the Virgo cluster will extend these results to a robust statistical framework., Comment: 17 pages, 10 figures, 2 tables, A&A in press

M49 (NGC 4472) is the dominant galaxy in subcluster B of the Virgo Cluster, and a benchmark for studying the build-up of the extended halos of brightest group galaxies in the outskirts of galaxy clusters. We investigate the kinematics in the outer halo of M49, look for substructures, and describe the transition to the surrounding intra-group light. As kinematic tracers we use planetary nebulae (PNe), combining kinematics from the extended Planetary Nebula Spectrograph (PN.S) early-type galaxy survey with our recent deep photometric sample. We study the position-velocity-plane for bright and faint PN populations out to 95 kpc radius, and employ a multi-Gaussian model for the velocity distribution to identify stellar populations with distinct kinematics and histories. We report the detection of stellar-kinematic substructure associated with the interaction of M49 with the dwarf irregular galaxy VCC 1249. We find two kinematically distinct PN populations associated with the main M49 halo and the extended intra-group light (IGL). These have velocity dispersions $\sigma_{halo}\simeq 170$ km/s and $\sigma_{IGL} \simeq400$ km/s at 10-80 kpc radii. The overall luminosity profile and velocity dispersion at $\sim80$ kpc are consistent with a flat circular velocity curve extrapolated from X-ray observations. The dispersion of the PNe associated with the IGL joins onto that of the satellite galaxies in subcluster B at $\sim100$ kpc radius. This is the first time that the transition from halo to IGL is observed based on the velocities of individual stars. Therefore the halo of M49, consisting of at least three distinct components, has undergone an extended accretion history within its parent group potential. The blue colours of the IGL component are consistent with a population of stars formed in low-mass galaxies at redshift $\sim0.5$ that has since evolved passively, as suggested by other data., Comment: 10 pages, 7 figures, accepted for publication in Astronomy & Astrophysics

As our closest cluster-neighbor, the Virgo cluster of galaxies is intensely studied by observers to unravel the mysteries of galaxy evolution within clusters. At this stage, cosmological numerical simulations of the cluster are useful to efficiently test theories and calibrate model. However, it is not trivial to select the perfect simulacrum of the Virgo cluster to fairly compare in detail its observed and simulated galaxy populations that are affected by the type and history of the cluster. Determining precisely the properties of Virgo for a later selection of simulated clusters becomes essential. It is still not clear how to access some of these properties such as the past history of the Virgo cluster from current observations. Therefore, directly producing effective simulacra of the Virgo cluster is inevitable. Efficient simulacra of the Virgo cluster can be obtained via simulations that resemble the local Universe down to the cluster scale. In such simulations, Virgo-like halos form in the proper local environment and permit assessing the most probable formation history of the cluster. Studies based on these simulations have already revealed that the Virgo cluster has had a quiet merging history over the last seven gigayears and that the cluster accretes matter along a preferential direction. This paper reveals that in addition such Virgo halos have had on average only one merger larger than about a tenth of their mass at redshift zero within the last four gigayears. This second branch (by opposition to main branch) formed in a given sub-region and merged recently (within the last gigayear). These properties are not shared with a set of random halos within the same mass range. This study extends [truncated], Accepted for publication in A&A, 10 pages, 8 figures

We determine abundance ratios of 37 dwarf ellipticals (dEs) in the nearby Virgo cluster. This sample is representative of the early-type population of galaxies in the absolute magnitude range -19.0 < Mr < -16.0. We analyze their absorption line-strength indices by means of index-index diagrams and scaling relations and use the stellar population models to interpret them. We present ages, metallicities and abundance ratios obtained from these dEs within an aperture size of Re/8. We calculate [Na/Fe] from NaD, [Ca/Fe] from Ca4227 and [Mg/Fe] from Mgb. We find that [Na/Fe] is under-abundant with respect to solar while [Mg/Fe] is around solar. This is exactly opposite to what is found for giant ellipticals, but follows the trend with metallicity found previously for the Fornax dwarf NGC 1396. We discuss possible formation scenarios that can result in such elemental abundance patterns and we speculate that dEs have disk-like SFH favouring them to originate from late-type dwarfs or small spirals. Na-yields appear to be very metal-dependent, in agreement with studies of giant ellipticals, probably due to the large dependence on the neutron-excess in stars. We conclude that dEs have undergone a considerable amount of chemical evolution, they are therefore not uniformly old, but have extended SFH, similar to many of the Local Group galaxies., 15 pages, 5 figures; accepted for publication in MNRAS

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band Halpha+[NII] imaging survey carried out with MegaCam at the Canada-France-Hawaii Telescope. The survey covers the whole Virgo cluster region from its core to one virial radius (104 deg^2). The sensitivity of the survey is of f(Halpha) ~ 4 x 10^-17 erg sec-1 cm^-2 (5 sigma detection limit) for point sources and Sigma (Halpha) ~ 2 x 10^-18 erg sec^-1 cm^-2 arcsec^-2 (1 sigma detection limit at 3 arcsec resolution) for extended sources, making VESTIGE the deepest and largest blind narrow-band survey of a nearby cluster. This paper presents the survey in all its technical aspects, including the survey design, the observing strategy, the achieved sensitivity in both the narrow-band Halpha+[NII] and in the broad-band r filter used for the stellar continuum subtraction, the data reduction, calibration, and products, as well as its status after the first observing semester. We briefly describe the Halpha properties of galaxies located in a 4x1 deg^2 strip in the core of the cluster north of M87, where several extended tails of ionised gas are detected. This paper also lists the main scientific motivations of VESTIGE, which include the study of the effects of the environment on galaxy evolution, the fate of the stripped gas in cluster objects, the star formation process in nearby galaxies of different type and stellar mass, the determination of the Halpha luminosity function and of the Halpha scaling relations down to ~ 10^6 Mo stellar mass objects, and the reconstruction of the dynamical structure of the Virgo cluster. This unique set of data will also be used to study the HII luminosity function in hundreds of galaxies, the diffuse Halpha+[NII] emission of the Milky Way at high Galactic latitude, and the properties of emission line galaxies at high redshift., Accepted for publication on Astronomy & Astrophysics

During pilot observations of the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Halpha+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the CFHT, we have observed the spiral galaxy NGC 4254 (M99). Deep Halpha+[NII] narrow-band and GALEX UV images revealed the presence of 60 compact (70-500 pc radius) star forming regions up to ~ 20 kpc outside the optical disc of the galaxy. These regions are located along a tail of HI gas stripped from the disc of the galaxy after a rapid gravitational encounter with another Virgo cluster member that simulations indicate occurred 280-750 Myr ago. We have combined the VESTIGE data with multifrequency data from the UV to the far-infrared to characterise the stellar populations of these regions and study the star formation process in an extreme environment such as the tails of stripped gas embedded in the hot intracluster medium. The colour, spectral energy distribution (SED), and linear size consistently indicate that these regions are coeval and have been formed after a single burst of star formation that occurred ~< 100 Myr ago. These regions might become free floating objects within the cluster potential well, and be the local analogues of compact sources produced after the interaction of gas-rich systems that occurred during the early formation of clusters., Accepted for publication on Astronomy & Astrophysics

We present results from Suzaku Key Project observations of the Virgo Cluster, the nearest galaxy cluster to us, mapping its X-ray properties along four long `arms' extending beyond the virial radius. The entropy profiles along all four azimuths increase with radius, then level out beyond $0.5r_{200}$, while the average pressure at large radii exceeds Planck Sunyaev-Zel'dovich measurements. These results can be explained by enhanced gas density fluctuations (clumping) in the cluster's outskirts. Using a standard Navarro, Frenk and White (1997) model, we estimate a virial mass, radius, and concentration parameter of $M_{200}=1.05\pm0.02\times10^{14}$ M$_\odot$, $r_{200}=974.1\pm5.7$ kpc, and $c = 8.8 \pm0.2$, respectively. The inferred cumulative baryon fraction exceeds the cosmic mean at $r\sim r_{200}$ along the major axis, suggesting enhanced gas clumping possibly sourced by a candidate large-scale structure filament along the north-south direction. The Suzaku data reveal a large-scale sloshing pattern, with two new cold fronts detected at radii of 233 kpc and 280 kpc along the western and southern arms, respectively. Two high-temperature regions are also identified 1 Mpc towards the south and 605 kpc towards the west of M87, likely representing shocks associated with the ongoing cluster growth. Although systematic uncertainties in measuring the metallicity for low temperature plasma remain, the data at large radii appear consistent with a uniform metal distribution on scales of $\sim 90\times180$ kpc and larger, providing additional support for the early chemical enrichment scenario driven by galactic winds at redshifts of 2-3., submitted to MNRAS

International audience; Early‐type dwarf galaxies are not simply featureless, old objects, but were found to be much more diverse, hosting substructures and a variety of stellar population properties. To explore the stellar content of faint early‐type galaxies, and to investigate in particular those with recent central star formation, we study colours and colour gradients within one effective radius in optical (g‐r) and near‐infrared (i‐H) bands for 120 Virgo cluster early‐type galaxies with 19 mag < M‐r < 16 mag. Twelve galaxies turn out to have blue cores, when defined as g‐r colour gradients larger than 0.10 mag/R‐eff, which represents the positive tail of the gradient distribution. For these galaxies, we find that they have the strongest age gradients, and that even outside the blue core, their mean stellar population is younger than the mean of ordinary faint early‐type galaxies. The metallicity gradients of these blue‐cored early‐type dwarf galaxies are, however, in the range of most normal faint early‐type galaxies, which we find to have non‐zero gradients with higher central metallicity. The blue central regions are consistent with star formation activity within the last few 100 Myr. We discuss whether these galaxies could be explained by environmental quenching of star formation in the outer galaxy regions while the inner star formation activity continued.

We study the star formation quenching mechanism in cluster galaxies by fitting the SED of the Herschel Reference Survey, a complete volume-limited K-band-selected sample of nearby galaxies including objects in different density regions, from the core of the Virgo cluster to the general field. The SED are fitted using the CIGALE SED modelling code. The truncated activity of cluster galaxies is parametrised using a specific SFH with 2 free parameters, the quenching age QA and the quenching factor QF. These 2 parameters are crucial for the identification of the quenching mechanism which acts on long timescales if starvation while rapid and efficient if ram pressure. To be sensitive to an abrupt and recent variation of the star formation activity, we combine in a new way 20 UV to FIR photometric bands with 3 age-sensitive Balmer line absorption indices extracted from available medium-resolution integrated spectroscopy and with Halpha narrow band imaging data. The use of a truncated SFH significantly increases the quality of the fit in those objects whose atomic gas content has been removed during the interaction with the hostile cluster environment. The typical QA of the perturbed late-type galaxies is QA < 300 Myr whenever the activity of star formation is reduced by 50% < QF 80%, while that of the quiescent early-types is QA ~ 1-3 Gyr. The fraction of late-types with a star formation activity reduced by QF > 80% and with an HI-deficiency parameter HI-def > 0.4 drops by a factor of ~ 5 from the inner half virial radius of the Virgo cluster, where the hot diffuse X-ray emitting gas of the cluster is located, to the outer regions. The efficient quenching of the star formation activity observed in Virgo suggests that the dominant stripping process is ram pressure. We discuss the implication of this result in the cosmological context of galaxy evolution., Accepted fro publication on Astronomy & Astrophysics

We present an analysis of high-quality photometry for globular clusters (GCs) in the Virgo cluster core region, based on data from the Next Generation Virgo Cluster Survey (NGVS) pilot field, and in the Milky Way (MW) based on VLT/X-Shooter spectrophotometry. We find significant discrepancies in color-color diagrams between sub-samples from different environments, confirming that the environment has a strong influence on the integrated colors of GCs. GC color distributions along a single color are not sufficient to capture the differences we observe in color-color space. While the average photometric colors become bluer with increasing radial distance to the cD galaxy M87, we also find a relation between the environment and the slope and intercept of the color-color relations. A denser environment seems to produce a larger dynamic range in certain color indices. We argue that these results are not due solely to differential extinction, IMF variations, calibration uncertainties, or overall age/metallicity variations. We therefore suggest that the relation between the environment and GC colors is, at least in part, due to chemical abundance variations, which affect stellar spectra and stellar evolution tracks. Our results demonstrate that stellar population diagnostics derived from model predictions which are calibrated on one particular sample of GCs may not be appropriate for all extragalactic GCs. These results advocate a more complex model of the assembly history of GC systems in massive galaxies that goes beyond the simple bimodality found in previous decades., 7 pages, 5 figures, accepted for publication in ApJ-Letters

We present measurements of the galaxy luminosity and stellar mass function in a 3.71 deg$^2$ (0.3 Mpc$^2$) area in the core of the Virgo cluster, based on $ugriz$ data from the Next Generation Virgo Cluster Survey (NGVS). The galaxy sample consists of 352 objects brighter than $M_g=-9.13$ mag, the 50% completeness limit of the survey. Using a Bayesian analysis, we find a best-fit faint end slope of $\alpha=-1.33 \pm 0.02$ for the g-band luminosity function; consistent results are found for the stellar mass function as well as the luminosity function in the other four NGVS bandpasses. We discuss the implications for the faint-end slope of adding 92 ultra compact dwarfs galaxies (UCDs) -- previously compiled by the NGVS in this region -- to the galaxy sample, assuming that UCDs are the stripped remnants of nucleated dwarf galaxies. Under this assumption, the slope of the luminosity function (down to the UCD faint magnitude limit, $M_g = -9.6$ mag) increases dramatically, up to $\alpha = -1.60 \pm 0.06$ when correcting for the expected number of disrupted non-nucleated galaxies. We also calculate the total number of UCDs and globular clusters that may have been deposited in the core of Virgo due to the disruption of satellites, both nucleated and non-nucleated. We estimate that ~150 objects with $M_g\lesssim-9.6$ mag and that are currently classified as globular clusters, might, in fact, be the nuclei of disrupted galaxies. We further estimate that as many as 40% of the (mostly blue) globular clusters in the core of Virgo might once have belonged to such satellites; these same disrupted satellites might have contributed ~40% of the total luminosity in galaxies observed in the core region today. Finally, we use an updated Local Group galaxy catalog to provide a new measurement of the luminosity function of Local Group satellites, $\alpha=-1.21\pm0.05$., Comment: ApJ, accepted

We analyze the kinematics of six Virgo cluster dwarf early-type galaxies (dEs) from their globular cluster (GC) systems. We present new Keck/DEIMOS spectroscopy for three of them and reanalyze the data found in the literature for the remaining three. We use two independent methods to estimate the rotation amplitude (Vmax) and velocity dispersion (sigma_GC) of the GC systems and evaluate their statistical significance by simulating non-rotating GC systems with the same number of GC satellites and velocity uncertainties. Our measured kinematics agree with the published values for the three galaxies from the literature and, in all cases, some rotation is measured. However, our simulations show that the null hypothesis of being non-rotating GC systems cannot be ruled out. In the case of VCC1861, the measured Vmax and the simulations indicate that it is not rotating. In the case of VCC1528, the null hypothesis can be marginally ruled out, thus, it might be rotating although further confirmation is needed. In our analysis, we find that, in general, the measured Vmax tends to be overestimated and the measured sigma_GC tends to be underestimated by amounts that depend on the intrinsic Vmax/sigma_GC, the number of observed GCs (N_GC), and the velocity uncertainties. The bias is negligible when N_GC>~20. In those cases where a large N_GC is not available, it is imperative to obtain data with small velocity uncertainties. For instance, errors of, ApJ in press. 20 pages, 17 figures, 5 tables

(Abridged) We investigate the intrinsic shapes of low-luminosity galaxies in the central 300 kpc of the Virgo cluster using deep imaging obtained as part of the NGVS. We build a sample of nearly 300 red-sequence cluster members in the yet unexplored $-14 < M_{g} < -8$ magnitude range. The observed distribution of apparent axis ratios is then fit by families of triaxial models with normally-distributed intrinsic ellipticities and triaxialities. We develop a Bayesian framework to explore the posterior distribution of the model parameters, which allows us to work directly on discrete data, and to account for individual, surface brightness-dependent axis ratio uncertainties. For this population we infer a mean intrinsic ellipticity E=0.43, and a mean triaxiality T=0.16. This implies that faint Virgo galaxies are best described as a family of thick, nearly oblate spheroids with mean intrinsic axis ratios 1:0.94:0.57. We additionally attempt a study of the intrinsic shapes of Local Group satellites of similar luminosities. For the LG population we infer a slightly larger mean intrinsic ellipticity E=0.51, and the paucity of objects with round apparent shapes translates into more triaxial mean shapes, 1:0.76:0.49. We finally compare the intrinsic shapes of NGVS low-mass galaxies with samples of more massive quiescent systems, and with field, star-forming galaxies of similar luminosities. We find that the intrinsic flattening in this low-luminosity regime is almost independent of the environment in which the galaxy resides--but there is a hint that objects may be slightly rounder in denser environments. The comparable flattening distributions of low-luminosity galaxies that have experienced very different degrees of environmental effects suggests that internal processes are the main drivers of galaxy structure at low masses--with external mechanisms playing a secondary role., Accepted to ApJ. 18 pages, 12 figures

The Virgo cluster is the largest Sunyaev-Zeldovich (SZ) source in the sky, both in terms of angular size and total integrated flux. Planck's wide angular scale and frequency coverage, together with its high sensitivity, allow a detailed study of this large object through the SZ effect. Virgo is well resolved by Planck, showing an elongated structure, which correlates well with the morphology observed from X-rays, but extends beyond the observed X-ray signal. We find a good agreement between the SZ signal (or Compton paranmeter, y_c) observed by Planck and the expected signal inferred from X-ray observations and simple analytical models. Due to its proximity to us, the gas beyond the virial radius can be studied with unprecedented sensitivity by integrating the SZ signal over tens of square degrees. We study the signal in the outskirts of Virgo and compare it with analytical models and a constrained simulation of the environment of Virgo. Planck data suggest that significant amounts of low-density plasma surround Virgo out to twice the virial radius. We find the SZ signal in the outskirts of Virgo to be consistent with a simple model that extrapolates the inferred pressure at lower radii while assuming that the temperature stays in the keV range beyond the virial radius. The observed signal is also consistent with simulations and points to a shallow pressure profile in the outskirts of the cluster. This reservoir of gas at large radii can be linked with the hottest phase of the elusive warm/hot intergalactic medium. Taking the lack of symmetry of Virgo into account, we find that a prolate model is favoured by the combination of SZ and X-ray data, in agreement with predictions., 21 pages and 20 figures. Submitted to A&A

We use the GALEX data of the GUViCS survey to construct the NUV luminosity function of the Virgo cluster over ~ 300 deg.2, an area covering the cluster and its surrounding regions up to ~ 1.8 virial radii. The NUV luminosity function is also determined for galaxies of different morphological type and NUV-i colour, and for the different substructures within the cluster. These luminosity functions are robust vs. statistical corrections since based on a sample of 833 galaxies mainly identified as cluster members with spectroscopic redshift (808) or high-quality optical scaling relations (10). We fit these luminosity functions with a Schechter function, and compare the fitted parameters with those determined for other nearby clusters and for the field. The faint end slope of the Virgo NUV luminosity function (alpha = -1.19), here sampled down to ~ NUV = -11.5 mag, is significantly flatter than the one measured in other nearby clusters and similar to the field one. Similarly M* = -17.56 is one-to-two magnitudes fainter than measured in Coma, A1367, the Shapley supercluster, and the field. These differences seem due to the quite uncertain statistical corrections and the small range in absolute magnitude sampled in these clusters. We do not observe strong systematic differences in the overall NUV luminosity function of the core of the cluster with respect to that of its periphery. We notice, however, that the relative contribution of red-to-blue galaxies at the faint end is inverted, with red quiescent objects dominating the core of the cluster and star forming galaxies dominating beyond one virial radius. These observational evidences are discussed in the framework of galaxy evolution in dense environments., Accepted for publication on Astronomy & Astrophsyics

International audience; Gas can be violently stripped from their galaxy disks in rich clusters, and be dispersed over 100kpc-scale tails or plumes. Young stars have been observed in these tails, suggesting they are formed in situ. This will contribute to the intracluster light, in addition to tidal stripping of old stars. We want to quantify the efficiency of intracluster star formation. We present CO(1--0) and CO(2--1) observations, made with the IRAM-30m telescope, towards the ram-pressure stripped tail northeast of NGC4388 in Virgo. HII regions found all along the tails, together with dust patches have been targeted. We detect molecular gas in 4 positions along the tail, with masses between 7x10$^5$ to 2x10$^6$ M$_\odot$. Given the large distance from the NGC 4388 galaxy, the molecular clouds must have formed in situ, from the HI gas plume. We compute the relation between surface densities of star formation and molecular gas in these regions, and find that the star formation has very low efficiency. The corresponding depletion time of the molecular gas can be up to 500 Gyr and more. Since this value exceeds a by far Hubble time, this gas will not be converted into stars, and will stay in a gaseous phase to join the intracluster medium.

International audience; We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo Cluster. Based on the specific stellar angular momentum lambda(Re) and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo Cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner 3 degrees (D \textless 1 Mpc) of the cluster. The fast rotators contain subtle disk-like structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo Cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between lambda(Re) and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram-pressure stripping, although some of it can be retained in their core, their star formation is quenched but their stellar kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.

We investigate a sample of 3 dwarf elliptical galaxies in the Virgo Cluster which have significant reservoirs of HI. We present deep optical imaging (from CFHT and KPNO), HI spectra (Arecibo) and resolved HI imaging (VLA) of this sample. These observations confirm their HI content and optical morphologies, and indicate that the gas is unlikely to be recently accreted. The sample has more in common with dwarf transitionals, although dwarf transitionals are generally lower in stellar mass and gas fraction. VCC 190 has an HI tidal tail from a recent encounter with the massive spiral galaxy NGC 4224. In VCC 611, blue star-forming features are observed which were unseen by shallower SDSS imaging., Comment: 11 pages, 6 figures, accepted in AJ

This study investigated the properties of the molecular gas content and star formation activity of 17 Virgo spirals, 21 Ursa Major (UMa) spirals, 13 Pisces spiral galaxies, and a comparison sample of 11 field spiral galaxies with a spatially resolved gas and stellar distribution. The H I-deficient galaxies with a defH I > 0.4 have a similar range of CO luminosity normalized by the K-band luminosity (L CO/L K) like the field spirals, although their CO content can be smaller by up to a factor of 2. The CO, H I, and stellar disk diameters are closely related to each other for both cluster and field galaxies, and the relative diameters of the CO and H I disks grow monotonically and smoothly as the H I-to-stellar disk diameter ratio decreases. Cluster galaxies have a molecular gas consumption time up to 10 times shorter than that of the field comparison sample, suggesting a significant change in the molecular gas content and star formation activity among all the cluster galaxies, even when they do not show any sign of H I stripping. The strongly H I-stripped Virgo cluster galaxies show only a modestly reduced total gas consumption time, indicating that the star formation activity and gas consumption are a highly local (rather than global) phenomenon. Our finding is that the depletion of cold gas by ram-pressure stripping and/or starvation caused by preprocessing in each cluster environment makes galaxies evolve passively.

In this paper we introduce the deepest and most extensive ultraviolet extragalactic source catalogs of the Virgo Cluster area to date. Archival and targeted GALEX imaging is compiled and combined to provide the deepest possible coverage over ~120 deg^2 in the NUV (lambda_eff=2316 angstroms) and ~40 deg^2 in the FUV (lambda_eff=1539 angstroms) between 180 deg 1 million Virgo Cluster sources), the Next Generation Virgo Cluster Survey (NGVS; >13 million Virgo Cluster sources), and the NED (~30,000 sources in the Virgo Cluster). We find 69% of the entire UV point-like source catalog has a unique optical counterpart, 11% of which are stars and 129 are Virgo cluster members neither in the VCC nor part of the bright CGCG galaxy catalog (i.e., m_pg < 14.5). These data are collected in four catalogs containing the UV extended sources, the UV point-like sources, and two catalogs each containing the most relevant optical parameters of UV-optically matched point-like sources for further studies from SDSS and NGVS. The GUViCS catalogs provide a unique set of data for future works on UV and multiwavelength studies in the cluster and background environments., 35 pages, 24 figures, 15 tables, Accepted for publication in A&A

We study the role of the environment on galaxy evolution using a sample of 868 galaxies in the Virgo cluster and in its surrounding regions selected from the GUViCS Survey with the purpose of understanding the origin of the red sequence in dense environments. We collected multifrequency data covering the whole electromagnetic spectrum for most of the galaxies. We identify the different dynamical substructures composing the Virgo cluster and we calculate the local density of galaxies using different methods. We then study the distribution of galaxies belonging to the red sequence, the green valley, and the blue cloud within the different cluster substructures. Our analysis indicates that all the most massive galaxies are slow rotators and are the dominant galaxies of the different cluster substructures generally associated with a diffuse X-ray emission. They are probably the result of major merging events that occurred at early epochs. Slow rotators of lower stellar mass are also preferentially located within the different high-density substructures of the cluster. They are virialised within the cluster, thus Virgo members since its formation. They have been shaped by gravitational perturbations occurring within the infalling groups that later formed the cluster. On the contrary, low-mass star-forming systems are extremely rare in the inner regions of the Virgo cluster A, where the density of the intergalactic medium is at its maximum. Our ram pressure stripping models consistently indicate that these star-forming systems can be rapidly deprived of their interstellar medium during their interaction with the intergalactic medium. The lack of gas quenches their star formation activity transforming them into quiescent dwarf ellipticals. This mild transformation does not perturb the kinematic properties of these galaxies which still have rotation curves typical of star-forming systems., Comment: Submitted for publication on Astronomy & Astrophysics

We present spatially resolved kinematics and global stellar populations and mass-to-light ratios for a sample of 39 dwarf early-type (dE) galaxies in the Virgo cluster studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. This sample is representative of the early-type population in the absolute magnitude range -19.0 < M_r < -16.0. For each dE, we measure the rotation curve and velocity dispersion profile and fit an analytic function to the rotation curve. We study the significance of the departure of the rotation curve from the best fit analytic function (poorly fit) and of the difference between the approaching and receding sides of the rotation curve (asymmetry). We find that 62 +/- 8 % (23 out of the 39) of the dEs have a significant anomaly in their rotation curve. Analysis of the images reveals photometric anomalies for most galaxies. However, there is no clear correlation between the significance of the photometric and kinematic anomalies. We measure age-sensitive and metallicity-sensitive Lick spectral indices and find a wide range of ages and metallicities. We also find that 4 dEs have emission partially filling in the Balmer absorption lines. Finally, we estimate the total masses and dark matter fractions of the dEs. They have a median total mass and dark matter fraction within the Re of log Me = 9.1 +/- 0.2 and f_DM = 46 +/- 18 %. We plot several scaling relations and show that dEs seem to be the bridge between massive early-type and dwarf spheroidal galaxies., Accepted for publication in ApJS. 49 pages, 71 figures, 8 tables

The HRS is a complete volume-limited sample of nearby objects including Virgo cluster and isolated objects. Using a recent compilation of HI and CO data we study the effects of the cluster on the molecular gas content of spiral galaxies. We first identify M* as the scaling variable that traces the total H2 mass of galaxies better. We show that, on average, HI-deficient galaxies are significantly offset from the M(H2) vs. M* relation for HI-normal galaxies. We use the M(H2) vs. M* scaling relation to define the H2-deficiency parameter. This parameter shows a weak and scattered relation with the HI-def, here taken as a proxy for galaxy interactions with the cluster environment. We also show that, as for the HI, the extent of the H2 disc decreases with increasing HI-deficiency. These results show that cluster galaxies have, on average, a lower H2 content than similar objects in the field. The slope of the H2-def vs. HI-def relation is less than 1, while the D(HI)/D(i) vs. HI-def relation is steeper than the D(CO)/D(i) vs. HI-def relation, thereby indicating that the H2 gas is removed less efficiently than the HI. This result can be understood if the HI is distributed on a flat disc more extended than the stellar disc, thus less anchored to the gravitational potential well of the galaxy than the H2. There is a clear trend between the NUV-i colour and H2-def, which suggests that H2 removal quenches the activity of star formation. This causes galaxies migrate from the blue cloud to the green valley and, eventually, to the red sequence. The total gas-consumption timescale of gas deficient cluster galaxies is comparable to that of isolated systems, and is significantly larger than the typical timescale for total gas removal in a ram pressure stripping process, thus suggesting that ram pressure, rather than starvation, is the dominant process driving the evolution of these cluster galaxies., Comment: Accepted for publication on A&A

We present the analysis of Halpha3, an Halpha imaging survey of 409 galaxies selected from the HI Arecibo ALFALFA Survey in the Local Supercluster, including the Virgo cluster. We explore the relations between the stellar mass, the HI mass and the current, massive SFR of nearby galaxies in the Virgo cluster and we compare them with those of isolated galaxies in the Local Supercluster, disentangling the role of the environment in shaping the star formation properties of galaxies at the present cosmological epoch. We investigate the relationships between atomic neutral gas and newly formed stars in different environments, across many morphological types, and over a wide range of stellar masses adopting an updated calibration of the HI deficiency parameter. Studying the mean properties of late-type galaxies in the Local Supercluster, we find that galaxies in increasing local galaxy density conditions (or decreasing projected angular separation from M87) show a significant decrease in the HI content and in the mean specific star formation rate, along with a progressive reddening of their stellar populations. The gradual quenching of the star formation occurs outside-in, consistently with the predictions of the ram pressure model. Once considered as a whole, the Virgo cluster is effective in removing neutral hydrogen from galaxies, and this perturbation is strong enough to appreciably reduce the SFR of its entire galaxy population. An estimate of the present infall rate of 300-400 galaxies per Gyr in the Virgo cluster is obtained from the number of existing HI-rich late-type systems, assuming 200-300 Myr as the time scale for HI ablation. If the infall process has been acting at constant rate this would imply that the Virgo cluster has formed approximately 2 Gyr ago, consistently with the idea that Virgo is in a young state of dynamical evolution., Comment: 13 pages, 10 figures, 4 tables, A&A accepted, language edited

We obtained using MegaCam at the CFHT a deep narrow band Halpha+[NII] wide field image of NGC 4569, the brightest late-type galaxy in the Virgo cluster. The image reveals the presence of long tails of diffuse ionised gas without any associated stellar component extending from the disc of the galaxy up to ~ 80 kpc (projected distance) with a typical surface brightness of a few 10^-18 erg s-1 cm-2 arcsec-2. These features provide direct evidence that NGC 4569 is undergoing a ram presure stripping event. The image also shows a prominent 8 kpc spur of ionised gas associated to the nucleus that spectroscopic data identify as an outflow. With some assumptions on the 3D distribution of the gas, we use the Halpha surface brightness of these extended low surface brightness features to derive the density and the mass of the gas stripped during the interaction of the galaxy with the ICM. The comparison with ad-hoc chemo-spectrophotometric models of galaxy evolution indicates that the mass of the Halpha emitting gas in the tail is comparable to that of the cold phase stripped from the disc, suggesting that the gas is ionised within the tail during the stripping process. The lack of star forming regions suggests that mechanisms other than photoionisation are responsible for the excitation of the gas (shocks, heat conduction, magneto hydrodynamic waves). This analysis indicates that ram pressure stripping is efficient in massive (M_star ~ 10^10.5 Mo) galaxies located in intermediate mass (~ 10^14 Mo) clusters under formation. It also shows that the mass of gas expelled by the nuclear outflow is ~ 1 % than that removed during the ram pressure stripping event. All together these results indicate that ram pressure stripping, rather than starvation through nuclear feedback, can be the dominant mechanism responsible for the quenching of the star formation activity of galaxies in high density environments., Comment: Accepted for publication on Astronomy & Astrophysics

We place our sample of 18 Virgo dwarf early-type galaxies (dEs) on the V-K - velocity dispersion, Faber-Jackson, and Fundamental Plane (FP) scaling relations for massive early-type galaxies (Es). We use a generalized velocity dispersion, which includes rotation, to be able to compare the location of both rotationally and pressure supported dEs with those of early and late-type galaxies. We find that dEs seem to bend the Faber-Jackson relation of Es to lower velocity dispersions, being the link between Es and dwarf spheroidal galaxies (dSphs). Regarding the FP relation, we find that dEs are significantly offset with respect to massive hot stellar systems, and re-casting the FP into the so-called kappa-space suggests that this offset is related to dEs having a total mass-to-light ratio higher than Es but still significantly lower than dSph galaxies. Given a stellar mass-to-light ratio based on the measured line indices of dEs, the FP offset allows us to infer that the dark matter fraction within the half light radii of dEs is on average >~ 42% (uncertainties of 17% in the K band and 20% in the V band), fully consistent with an independent estimate in an earlier paper in this series. We also find that dEs in the size-luminosity relation in the near-infrared, like in the optical, are offset from early-type galaxies, but seem to be consistent with late-type galaxies. We thus conclude that the scaling relations show that dEs are different from Es, and that they further strengthen our previous findings that dEs are closer to and likely formed from late-type galaxies., 14 pages, 9 figures, 2 appendixes. Accepted for publication in A&A

The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) is a complete blind survey of the Virgo cluster covering about 40 sq. deg. in the far UV (FUV, lambda_eff=1539A, Delta-lambda=442A) and about 120 sq. deg. in the near UV (NUV, lambda_eff=2316A, Delta-lambda=1060A). The goal of the survey is to study the ultraviolet (UV) properties of galaxies in a rich cluster environment, spanning a wide luminosity range from giants to dwarfs, and regardless of prior knowledge of their star formation activity. The UV data will be combined with those in other bands (optical: NGVS; far-infrared - submm: HeViCS; HI: ALFALFA) and with our multizone chemo-spectrophotometric models of galaxy evolution to make a complete and exhaustive study of the effects of the environment on the evolution of galaxies in high density regions. We present here the scientific objectives of the survey, describing the observing strategy and briefly discussing different data reduction techniques. Using UV data already in-hand for the central 12 sq. deg. we determine the FUV and NUV luminosity functions of the Virgo cluster core for all cluster members and separately for early- and late-type galaxies and compare it to the one obtained in the field and other nearby clusters (Coma, A1367). This analysis shows that the FUV and NUV luminosity functions of the core of the Virgo clusters are flatter (alpha about -1.1) than those determined in Coma and A1367. We discuss the possible origin of this difference, 18 pages, 14 figures, accepted in A&A, high resolution version of figure 1 and 2 and other information available at http://galex.oamp.fr/guvics/observations.html

We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster, obtained with the WHT and INT telescopes at the Roque de los Muchachos Observatory (La Palma, Spain). These data are used to study the origin of the dwarf elliptical galaxy population inhabiting clusters. We confirm that dEs are not dark matter dominated galaxies, at least up to the half-light radius. We also find that the observed galaxies in the outer parts of the cluster are mostly rotationally supported systems with disky morphological shapes. Rotationally supported dEs have rotation curves similar to those of star forming galaxies of similar luminosity and follow the Tully-Fisher relation. This is expected if dE galaxies are the descendant of low luminosity star forming systems which recently entered the cluster environment and lost their gas due to a ram pressure stripping event, quenching their star formation activity and transforming into quiescent systems, but conserving their angular momentum., 24 pages, 15 figures and 7 tables. Replaced to match the journal version

Ram pressure stripping of the multiphase ISM is studied in the perturbed Virgo cluster spiral galaxy NGC 4438. This galaxy underwent a tidal interaction ~100 Myr ago and is now strongly affected by ram pressure stripping. Deep VLA radio continuum observations at 6 and 20 cm are presented. We detect prominent extraplanar emission to the west of the galactic center, which extends twice as far as the other tracers of extraplanar material. The spectral index of the extraplanar emission does not steepen with increasing distance from the galaxy. This implies in situ re-acceleration of relativistic electrons. The comparison with multiwavelength observations shows that the magnetic field and the warm ionized interstellar medium traced by Halpha emission are closely linked. The kinematics of the northern extraplanar Halpha emission, which is ascribed to star formation, follow those of the extraplanar CO emission. In the western and southern extraplanar regions, the Halpha measured velocities are greater than those of the CO lines. We suggest that the ionized gas of this region is excited by ram pressure. The spatial and velocity offsets are consistent with a scenario where the diffuse ionized gas is more efficiently pushed by ram pressure stripping than the neutral gas. We suggest that the recently found radio-deficient regions compared to 24 mum emission are due to this difference in stripping efficiency., Comment: 8 pages, 6 figures, A&A, accepted for publication

High sensitivity 21-cm H I line observations with an rms noise level of similar to 0.5 mJy were made of 35 spiral galaxies in the Coma Supercluster, using the refurbished Arecibo telescope, leading to detection of 25 objects. These data, combined with the measurements available in the literature, provide the set of H I data for 94% of all late-type galaxies in the Coma Supercluster with an apparent photographic magnitude m(p)

We present the Halpha imaging observations of 273 late-type galaxies in the nearby rich galaxy clusters Virgo, A1367, Coma, Cancer, Hercules and in the Great Wall, carried out primarily with the 2.1m telescope of the San Pedro Martir Observatory (SPM) and with the ESO/3.6m telescope. We derived the Halpha+[NII] fluxes and equivalent widths. The Halpha survey reached completion for an optically selected sample of nearby galaxies in and outside rich clusters. Taking advantage of the completeness of the data set, the dependence of Halpha properties on the Hubble type was determined for late-type galaxies in the Virgo cluster. Differences in the gaseous content partly account for the large scatter of the Halpha E.W. within each Hubble-type class. We studied the radial distributions of the Halpha E.W. around Coma+A1367 and the Virgo clusters in two luminosity bins. Luminous galaxies show a decrease in their average Halpha E.W. in the inner 1 virial radius, while low-luminosity galaxies do not show this trend., 16 pages, 9 figures, 2 tables. Accepted for publication on A&A. Data and Fits images available at http://goldmine.mib.infn.it

We report on a complete CCD imaging survey of 226 elliptical galaxies in the North-East quadrant of the Virgo cluster, representative of the properties of giant and dwarf elliptical galaxies in this cluster. We fit their radial light profiles with the Sersic r^(1/n) model of light distribution. We confirm the result of Graham & Guzman (2003) that the apparent dichotomy between E and dE galaxies in the luminosity-_e plane no longer appears when other structural parameters are considered and can be entirely attributed to the onset of "core" galaxies at B_T sim -20.5 mag. When "core" galaxies are not considered, E and dE form a unique family with n linearly increasing with the luminosity. For 90 galaxies we analyze the B-I color indices, both in the nuclear and in the outer regions. Both indices are bluer toward fainter luminosities. We find also that the outer color gradients do not show any significant correlation with the luminosity. The scatter in all color indicators increases significantly toward lower luminosities, e.g. galaxies fainter than B_T sim -15 have a B-I spread 0.5 mag., 21 pages, 14 figures, 2 tables. Accepted for publication on A&A. High resolution figures at http://goldmine.mib.infn.it/papers/WFS_04/WFS_04-frame.html

Not Available

We present evidence for kinematically decoupled cores (KDCs) in two dwarf early-type (dE) galaxies in the Virgo cluster, VCC 1183 and VCC 1453, studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. These KDCs have radii of 1.8'' (0.14 kpc) and 4.2'' (0.33 kpc), respectively. Each of these KDCs is distinct from the main body of its host galaxy in two ways: (1) inverted sense of rotation; and (2) younger (and possibly more metal-rich) stellar population. The observed stellar population differences are probably associated with the KDC, although we cannot rule out the possibility of intrinsic radial gradients in the host galaxy. We describe a statistical analysis method to detect, quantify the significance of, and characterize KDCs in long-slit rotation curve data. We apply this method to the two dE galaxies presented in this paper and to five other dEs for which KDCs have been reported in the literature. Among these seven dEs, there are four significant KDC detections, two marginal KDC detections, and one dE with an unusual central kinematic anomaly that may be an asymmetric KDC.The frequency of occurence of KDCs and their properties provide important constraints on the formation history of their host galaxies. We discuss different formation scenarios for these KDCs in cluster environments and find that dwarf-dwarf wet mergers or gas accretion can explain the properties of these KDCs. Both of these mechanisms require that the progenitor had a close companion with a low relative velocity. This suggests that KDCs were formed in galaxy pairs residing in a poor group environment or in isolation whose subsequent infall into the cluster quenched star formation., 14 pages, accepted for publication in ApJ