MICADO is a first light instrument for the Extremely Large Telescope (ELT), set to start operating later this decade. It will provide diffraction limited imaging, astrometry, high contrast imaging, and long slit spectroscopy at near-infrared wavelengths. During the initial phase operations, adaptive optics (AO) correction will be provided by its own natural guide star wavefront sensor. In its final configuration, that AO system will be retained and complemented by the laser guide star multi-conjugate adaptive optics module MORFEO (formerly known as MAORY). Among many other things, MICADO will study exoplanets, distant galaxies and stars, and investigate black holes, such as Sagittarius A* at the centre of the Milky Way. After their final design phase, most components of MICADO have moved on to the manufacturing and assembly phase. Here we summarize the final design of the instrument and provide an overview about its current manufacturing status and the timeline. Some lessons learned from the final design review process will be presented in order to help future instrumentation projects to cope with the challenges arising from the substantial differences between projects for 8-10m class telescopes (e.g. ESO-VLT) and the next generation Extremely Large Telescopes (e.g. ESO-ELT). Finally, the expected performance will be discussed in the context of the current landscape of astronomical observatories and instruments. For instance, MICADO will have similar sensitivity as the James Webb Space Telescope (JWST), but with six times the spatial resolution.

We use optical integral field spectroscopy from VLT/MUSE, as well as photometric observations from Hubble Space Telescope and VLT/HAWK-I, to study the morpho-kinematics of 17 low-mass (log(M/M⊙) < 9.5) MACS J0416.1-2403 cluster galaxies at R200 and five field galaxies with a redshift of z ∼ 0.4. By measuring fluxes of strong emission lines from the MUSE data, we have recovered the star formation rates, gas-phase metallicities, and spatially resolved gas kinematics, and we have also investigated the ionising mechanisms. We have analysed the structure and morphology of the galaxies from the optical and infrared photometric data, performing a multi-component decomposition into a bulge and a disk. The spatially resolved gas velocity fields of the cluster members and field galaxies were modelled using a 3D approach, which allowed us to retrieve their intrinsic gas kinematics, including the maximum rotation velocity and velocity dispersion. This enabled us to study scaling relations such as the Tully–Fisher and the stellar mass–S0.5 relation for low-mass galaxies in different environments and to search for signatures of cluster-specific processes using disturbed gas velocity fields as tracers. Most galaxies from our sample fall in the star-forming and composite region in the diagnostic diagram, which allows for the ionising sources in a galaxy to be disentangled. The cluster and field population can be classified as star-forming main-sequence galaxies, with only a sub-sample of four quenched systems. We observe significant scatter for the cluster galaxies in the mass-metallicity plane, and the lowest-mass systems deviate from the predictions of the fundamental metallicity relation, showing higher metallicities, whereas the higher-mass ones are in accordance with the model predictions. This might hint at the cutoff of pristine gas inflow and/or the removal of the hot halo gas as the mechanisms driving these offsets. Our morpho-kinematic analysis reveals a sub-sample of dwarfs with maximum velocities vmax < 50 km s−1 and vmax, gas/σgas < 1, which depart from the Tully–Fisher relation. This might indicate that their interstellar medium is affected by external environmental processes, such as ram pressure stripping. However, ∼30% of the cluster galaxies have rotation-dominated gas disks and follow the Tully–Fisher relation within 1σ. Using the S0.5 parameter, which links the dynamical support of ordered motions with that of random motions, we can differentiate between galaxies affected by gravitational processes and systems affected by hydrodynamical ones. In the stellar mass–S0.5 plane, both cluster and field galaxies follow a tight sequence, with only a sub-population of five galaxies strongly departing (> 4σ) from this relation, showing high σgas values. Both the morphology and kinematics of the outlier galaxies hint at a combination of pre-processing and cluster-specific interactions affecting their stellar and gas disks.

We present new gas kinematic observations with the OSIRIS instrument at the GTC for galaxies in the Cl1604 cluster system at z=0.9. These observations together with a collection of other cluster samples at different epochs analyzed by our group are used to study the evolution of the Tully-Fisher, velocity-size and stellar mass-angular momentum relations in dense environments over cosmic time. We use 2D and 3D spectroscopy to analyze the kinematics of our cluster galaxies and extract their maximum rotation velocities (Vmax). Our methods are consistently applied to all our cluster samples which make them ideal for an evolutionary comparison. Up to redshift one, our cluster samples show evolutionary trends compatible with previous observational results in the field and in accordance with semianalytical models and hydrodynamical simulations concerning the Tully-Fisher and velocity-size relations. However, we find a factor 3 drop in disk sizes and an average B-band luminosity enhancement of 2 mag by z=1.5. We discuss the role that different cluster-specific interactions may play in producing this observational result. In addition, we find that our intermediate-to-high redshift cluster galaxies follow parallel sequences with respect to the local specific angular momentum-stellar mass relation, although displaying lower angular momentum values in comparison with field samples at similar redshifts. This can be understood by the stronger interacting nature of dense environments with respect to the field.

We reveal the importance of ongoing in situ star formation in the brightest cluster galaxy (BCG) in the massive cool-core CLASH cluster MACS 1931.8-2635 at a redshift ofz = 0.35 by analysing archival VLT-MUSE optical integral field spectroscopy. Using a multi-wavelength approach, we assessed the stellar and warm ionised medium components, which were spatially resolved by the VLT-MUSE spectroscopy, and linked them to the molecular gas by incorporating sub-mm ALMA observations. We measured the fluxes of strong emission lines such as: [O II]λ3727, Hβ, [O III]λ5007, Hα, [N II]λ6584, and [S II]λ6718, 6732, which allowed us to determine the physical conditions of the warm ionised gas, such as electron temperature, electron density, extinction, ionisation parameter, (O/H) gas metallicities, star formation rates, and gas kinematics, as well as the star formation history of the system. Our analysis reveals the ionising sources in different regions of the galaxy. The ionised gas flux brightness peak corresponds to the location of the supermassive black hole in the BCG and the system shows a diffuse warm ionised gas tail extending 30 kpc in the north-east direction. The ionised and molecular gas are co-spatial and co-moving, with the gaseous component in the tail likely falling inward, providing fuel for star formation and accretion-powered nuclear activity. The gas is ionised by a mix of star formation and other energetic processes which give rise to LINER-like emission, with active galactic nuclei emission dominant only in the BCG core. We measured a star formation rate of ∼97 M⊙yr−1, with its peak at the BCG core. However, star formation accounts for only 50–60% of the energetics needed to ionise the warm gas. The stellar mass growth of the BCG atz < 0.5 is dominated either by in situ star formation generated by thermally unstable intracluster medium cooling or by dry mergers, with these mechanisms accounting for the build-up of 20% of the stellar mass of the system. Our measurements reveal that the most central regions of the BCG contain the lowest gas-phase oxygen abundance, whereas the Hαarm exhibits slightly more elevated values, suggesting the transport of gas out to large distances from the centre as a result of active galactic nuclei outbursts. The galaxy is a dispersion-dominated system that is typical for massive, elliptical galaxies. The gas and stellar kinematics are decoupled, with the gaseous velocity fields being more closely related to the bulk motions of the intracluster medium.

We present optical VLT/MUSE integral field spectroscopy data of the merging galaxy NGC 1487. We use fitting techniques to study the ionized gas emission of this merger and its main morphological and kinematical properties. We measured flat and sometimes inverted oxygen abundance gradients in the subsystems composing NGC 1487, explained by metal mixing processes common in merging galaxies. We also measured widespread star-forming bursts, indicating that photoionisation by stars is the primary ionization source of the galaxy. The kinematic map revealed a rotating pattern in the gas in the northern tail of the system, suggesting that the galaxy may be in the process of rebuilding a disc. The gas located in the central region has larger velocity dispersion (σ ≈ 50 km s−1) than the remaining regions, indicating kinematic heating, possibly owing to the ongoing interaction. Similar trends were, however, not observed in the stellar velocity-dispersion map, indicating that the galaxy has not yet achieved equilibrium, and the nebular and stellar components are still kinematically decoupled. Based on all our measurements and findings, and specially on the mass estimates, metallicity gradients and velocity fields of the system, we propose that NGC 1487 is the result of an ongoing merger event involving smallish dwarf galaxies within a group, in a pre-merger phase, resulting in a relic with mass and physical parameters similar to a dwarf galaxy. Thus, we may be witnessing the formation of a dwarf galaxy by merging of smaller clumps at z=0.

Aims. While many aspects of the impact of dense environments on late-type galaxies at redshifts below unity have been scrutinized in the past few decades, observational studies of the interplay between environment and disk galaxy evolution at z > 1 are still scarce. We observed star-forming galaxies at z ≈ 1.5 selected from the HyperSuprimeCam Subaru Strategic Program. The galaxies are part of two significant overdensities of [O II] emitters identified via narrowband imaging and photometric redshifts from grizy photometry. Methods. We used the K-band Multi-Object Spectrograph (KMOS) to carry out Hα integral field spectroscopy of 46 galaxies in total. Ionized gas maps, star formation rates, and velocity fields were derived from the Hα emission line. We quantified morphological and kinematical asymmetries in order to look for potential gravitational (e.g., galaxy-galaxy) or hydrodynamical (e.g., ram-pressure) interactions. Results. Hα emission was detected in 36 of our targets. Of these galaxies, 34 are members of two (proto-)clusters at z = 1.47, confirming our selection strategy to be highly efficient. By fitting model velocity fields to the observed ones, we determined the intrinsic maximum rotation velocity Vmax of 14 galaxies. Utilizing the luminosity–velocity (Tully–Fisher) relation, we find that these galaxies are more luminous than their local counterparts of similar mass by up to ∼4 mag in the rest-frame B-band. In contrast to field galaxies at z < 1, the offsets of the z ≈ 1.5 (proto-)cluster galaxies from the local Tully–Fisher relation are not correlated with their star formation rates but with the ratio between Vmax and gas velocity dispersion σg. This probably reflects that fewer disks have settled to purely rotational kinematics and high Vmax/σg ratios, as is observed in the field at similar redshifts. Tests with degraded low-redshift cluster galaxy data show that we cannot identify purely hydrodynamical interactions with the imaging currently at hand. Due to relatively low galaxy velocity dispersions (σv < 400 km s−1) of the (proto-)clusters, gravitational interactions are likely more efficient, resulting in higher kinematical asymmetries than in present-days clusters.

Aims. In order to understand the role of the different processes that drive galaxy evolution in clusters, we need comprehensive studies that simultaneously examine several of the most important physical properties of galaxies. In this work we study the interplay between the kinematic state and star formation activity of galaxies in the RXJ1347−1145 cluster complex at z ∼ 0.45. Methods. We used VLT/VIMOS to obtain slit spectra for 95 galaxies across the 40′ × 40′ area where the RXJ1347−1145 cluster complex resides. We determined the cluster membership of our targets by identifying one or more of the available emission lines within the wavelength range. Our spectroscopy is complemented with archival SUBARU/Suprime-Cam deep photometric observations in five optical bands (B, V, Rc, Ic, z′). We examined the kinematic properties of our sample attending to the degree of distortion of the extracted rotation curves. Regular rotating galaxies were included in our Tully–Fisher analysis while the distorted ones were used to study the role of cluster-specific interactions with respect to star formation and AGN activity. Results. Our analysis confirmed the cluster membership for approximately half of our targets. We report a higher fraction of galaxies with irregular gas kinematics in the cluster environment than in the field. Cluster galaxies with regular rotation display a moderate brightening in the B-band Tully–Fisher relation compatible with the gradual evolution of the stellar populations with lookback time, and no significant evolution in the stellar-mass Tully–Fisher relation, in line with previous studies at similar redshift. Average specific star formation rate values are slightly lower in our cluster sample (−0.15 dex) with respect to the main sequence of star-forming galaxies, confirming the role of the environment in the early quenching of star formation in clusters. Finally, we carried out an exploratory observational study on the stellar-to-halo mass relation finding that cluster galaxies tend to have slightly lower stellar mass values for a fixed halo mass compared to their field counterparts.

ScopeSim is a flexible multipurpose instrument data simulation framework built in Python. It enables both raw and reduced observation data to be simulated for a wide range of telescopes and instruments quickly and efficiently on a personal computer. The software is currently being used to generate simulated raw input data for developing the data reduction pipelines for the MICADO and METIS instruments at the ELT. The ScopeSim environment consists of three main packages which are responsible for providing on-sky target templates (ScopeSim_templates), the data to build the optical models of various telescopes and instruments (instrument reference database), and the simulation engine (ScopeSim). This strict division of responsibilities allows ScopeSim to be used to simulate observation data for many different instrument and telescope configurations for both imaging and spectroscopic instruments. ScopeSim has been built to avoid redundant calculations where ever possible. As such it is able to deliver simulated observations on time scales of seconds to minutes. All the code and data is open source and hosted on Github. The community is also most welcome, and indeed encouraged to contribute to code ideas, target templates, and instrument packages.

Aims. Gas-phase metallicities offer insight into the chemical evolution of galaxies as they reflect the recycling of gas through star formation and galactic inflows and outflows. Environmental effects such as star-formation quenching mechanisms play an important role in shaping the evolution of galaxies. Clusters of galaxies at z < 0.5 are expected to be the sites where environmental effects can be clearly observed with present-day telescopes. Methods. We explored the Frontier Fields cluster RX J2248−443 at z = 0.348 with VIMOS/VLT spectroscopy from CLASH-VLT, which covers a central region corresponding to almost 2 virial radii. The fluxes of [OII] λ 3727, H β , [OIII] λ 5007, H α and [NII] λ 6584 emission lines were measured allowing the derivation of (O/H) gas metallicities, star formation rates based on extinction-corrected H α fluxes, and contamination from active galactic nuclei. We compared our sample of cluster galaxies to a population of field galaxies at similar redshifts. Results. We use the location of galaxies in projected phase-space to distinguish between cluster and field galaxies. Both populations follow the star-forming sequence in the diagnostic diagrams, which allow the ionising sources in a galaxy to be disentangled, with only a low number of galaxies classified as Seyfert II. Both field and cluster galaxies follow the “main sequence” of star-forming galaxies, with no substantial difference observed between the two populations. In the mass–metallicity (MZ) plane, both high-mass field and cluster galaxies show comparable (O/H)s to the local SDSS MZ relation, with an offset of low-mass galaxies (log( M / M ⊙ ) < 9.2) towards higher metallicities. While both the metallicities of “accreted” ( R < R 500 ) and “infalling” ( R > R 500 ) cluster members are comparable at all masses, the cluster galaxies from the “mass complete” bin (which is the intermediate mass bin in this study: 9.2 < log( M / M ⊙ ) < 10.2), show more enhanced metallicities than their field counterparts by a factor of 0.065 dex with a ∼1.8 σ significance. The intermediate-mass field galaxies are in accordance with the expected (O/H)s from the fundamental metallicity relation, while the cluster members deviate strongly from the model predictions, namely by a factor of ∼0.12 dex. The results of this work are in accordance with studies of other clusters at z < 0.5 and favour the scenario in which the hot halo gas of low- and intermediate-mass cluster galaxies is removed due to ram pressure stripping, leading to an increase in their gas-phase metallicity.

The analysis of a cluster environment is a valuable instrument to investigate the origin of gas fuelling and trigger mechanisms in active galactic nuclei (AGN) and star-forming galaxies. To this purpose, we present a detailed analysis of the point-like X-ray sources in the Bullet cluster field. Based on ∼600 ks Chandra observations, we produced a catalogue of 381 X-ray point sources up to a distance of ∼1.5 virial radius and with flux limits ∼1 × 10−16 and ∼8 × 10−16 erg cm−2 s−1 in the 0.5–2 keV and 2–10 keV bands, respectively. We find a strong (up to a factor 1.5–2) and significant (≥4σ) over-density in the full region studied 0.3R200 < R < 1.5R200. We identified optical (R band) and infrared (Spitzer IRAC) counterparts for ∼84% and ∼48% of the X-ray sources, respectively. We obtained new spectroscopic redshifts for 106 X-ray sources and collected from the literature additional 13 spectroscopic and 8 photometric redshifts of X-ray sources. Twenty-nine X-ray sources turned out to be cluster members. Spectroscopic and photometric redshifts of optical and infrared sources were also collected, and these sources were used as ancillary samples. We used these multi-wavelength data to characterise the nature of the Bullet cluster X-ray point sources. We find that the over-density in the region 0.3R200 < R < R200 is likely due to X-ray AGN (mostly obscured) and star-forming galaxies associated with the cluster, while in the more external region this over-density is likely to be mostly due to background AGN. The fraction of cluster galaxies hosting an X-ray detected AGN is 1.0 ± 0.4%, which is nearly constant with the radius; this fraction is similar to that reported in other clusters of galaxies at similar redshift. The fraction of X-ray bright AGN (L2 − 10 keV > 1043 ergs s−1) in the region 0.3R200 < R < R200 is 0.5−0.2+0.6%, which is higher than that in other clusters at similar redshift and more similar to the AGN fraction in the field. Finally, the spatial distributions of AGN and star-forming galaxies, which we selected for their infrared emission, appear similar, thus suggesting that both are triggered by the same mechanism.

We carry out a detailed strong lensing analysis of a sub-sample of eight galaxy clusters of the CLASH survey, in the redshift range of $ z_{\rm cluster} = [0.23-0.59]$, using extensive spectroscopic information, primarily MUSE archival data complemented with CLASH-VLT redshift measurements. Different models are tested in each cluster depending on the complexity of its mass distribution and on the number of detected multiple images. Four clusters show more than five spectroscopically confirmed multiple image families. In this sample, we do not make use of families that are only photometrically identified, in order to reduce model degeneracies and systematics due to the potential misidentifications of some multiple images. We present spectroscopic confirmation of 27 multiply lensed sources, with no previous spectroscopic measurements, spanning over the redshift range of $z_{\rm src}=[0.7-6.1]$. Moreover, we confirm an average of $48$ galaxy members in the core of each cluster, thanks to the high efficiency and large field of view of MUSE. Despite having different properties (i.e., number of mass components, total mass, redshift, etc), the projected total mass and mass density profiles of all clusters have very similar shapes, when rescaled by independent measurements of $M_{200c}$ and $R_{200c}$. Specifically, we measure the mean value of the projected total mass of our cluster sample within 10 (20)% of $R_{200c}$ to be 0.13 (0.32) of $M_{200c}$, with a remarkably small scatter of 5 (6)%. Furthermore, the large number of high-z sources and the precise magnification maps derived in this work for four clusters add up to the sample of high-quality gravitational telescopes to be used to study the faint and distant Universe. The strong lensing models and the full redshift catalogues from MUSE are publicly available.

Context. The study of the galaxy stellar mass function (SMF) in relation to the galaxy environment and the stellar mass density profile, ρ (r), is a powerful tool to constrain models of galaxy evolution. Aims. We determine the SMF of the z = 0.44 cluster of galaxies MACS J1206.2-0847 separately for passive and star-forming (SF) galaxies, in different regions of the cluster, from the center out to approximately 2 virial radii. We also determine ρ (r) to compare it to the number density and total mass density profiles. Methods. We use the dataset from the CLASH-VLT survey. Stellar masses are obtained by spectral energy distribution fitting with the MAGPHYS technique on 5-band photometric data obtained at the Subaru telescope. We identify 1363 cluster members down to a stellar mass of 109.5 M , selected on the basis of their spectroscopic (∼1/3 of the total) and photometric redshifts. We correct our sample for incompleteness and contamination by non members. Cluster member environments are defined using either the clustercentric radius or the local galaxy number density. Results. The whole cluster SMF is well fitted by a double Schechter function, which is the sum of the two Schechter functions that provide good fits to the SMFs of, separately, the passive and SF cluster populations. The SMF of SF galaxies is significantly steeper than the SMF of passive galaxies at the faint end. The SMF of the SF cluster galaxies does not depend on the environment. The SMF of the passive cluster galaxies has a significantly smaller slope (in absolute value) in the innermost (≤0.50 Mpc, i.e.,∼0.25 virial radii), and in the highest density cluster region than in more external, lower density regions. The number ratio of giant/subgiant galaxies is maximum in this innermost region and minimum in the adjacent region, but then gently increases again toward the cluster outskirts. This is also reflected in a decreasing radial trend of the average stellar mass per cluster galaxy. On the other hand, the stellar mass fraction, i.e., the ratio of stellar to total cluster mass, does not show any significant radial trend. Conclusions. Our results appear consistent with a scenario in which SF galaxies evolve into passive galaxies due to density-dependent environmental processes and eventually get destroyed very near the cluster center to become part of a diffuse intracluster medium. Dynamical friction, on the other hand, does not seem to play an important role. Future investigations of other clusters of the CLASHVLT sample will allow us to confirm our interpretation.

Aims . Color gradients of galaxies are a powerful tool for resolving the variations of stellar populations within galaxies. We use this approach to explore the evolution of early-type galaxies in the core of the massive galaxy cluster MACS J1206.2-0847 at z = 0.44. Methods . We used imaging data in 12 filters (covering a wavelength range from 400 to 1600 nm) from the Hubble Space Telescope provided by the CLASH survey, as well as additional spectral information from its follow-up program, CLASH-VLT. We performed multiwavelength optimized model fitting using Galapagos-2 from the MegaMorph project to measure their photometric parameters (total integrated magnitudes, effective radii r e , and Sérsic indices n ). We used them to derive color gradients for the colors g 475 − I 814 , r 625 − Y 105 , I 814 − H 160 , and Y 105 − H 160 at radii ranging between 0.1 and 2 r e for 79 early-type cluster galaxies. From synthetic spectral models that use simple star formation recipes, we inferred ages and metallicities of the stellar population at different locations within each galaxy and characterized their influence on the radial color trends. Results . Early-type galaxies show a substantial decrease in effective radii r e with wavelength. We measure that galaxy sizes are ~25% smaller in the red H 160 filter than in the blue r 625 filter but maintain a constant (within 3 σ ) Sérsic index n with wavelength. We find negative color gradients in all colors with slopes ranging between −0.07 and −0.17 mag dex −1 and with no obvious dependence on total magnitude, stellar mass, or location inside the cluster core. We explain the observed radial trends of color gradients as a result of the ages and metallicities of the respective stellar populations. Red galaxy cores are typically ~3 Gyr older and more enriched in metals than the galaxy outskirts, which are of solar metallicity. Conclusions . Our results support the predictions from hydrodynamical cosmological simulations, which describe a passive evolution combined with an inside-out-growth of early-type galaxies. In this scenario, galaxies assemble their stellar mass primarily in the outskirts through the accretion of mass-poor satellites and thus manifest the observed trends of color-, metallicity- and age gradients.

Context: The galaxy cluster Abell S1101 (S1101 hereafter) deviates significantly from the X-ray luminosity versus velocity dispersion relation (L-sigma) of galaxy clusters in our previous study. Given reliable X-ray luminosity measurement combining XMM-Newton and ROSAT, this could most likely be caused by the bias in the velocity dispersion due to interlopers and low member statistic in the previous sample of member galaxies, which was solely based on 20 galaxy redshifts drawn from the literature. Aims: We intend to increase the galaxy member statistic to perform a precision measurement of the velocity dispersion and dynamical mass of S1101. We aim for a detailed substructure and dynamical state characterization of this cluster, and a comparison of mass estimates derived from (i) the velocity dispersion (M_vir), (ii) the caustic mass computation (M_caustic), and (iii) mass proxies from X-ray observations and the Sunyaev-Zeldovich (SZ) effect. Methods: We carried out new optical spectroscopic observations of the galaxies in this cluster field with VIMOS, obtaining a sample of ~60 member galaxies for S1101. We revised the cluster redshift and velocity dispersion measurements based on this sample and also applied the Dressler-Shectman substructure test. Results: The completeness of cluster members within r200 was significantly improved for this cluster. Tests for dynamical substructure did not show evidence for major disturbances or merging activities in S1101. We find good agreement between the dynamical cluster mass measurements and X-ray mass estimates which confirms the relaxed state of the cluster displayed in the 2D substructure test. The SZ mass proxy is slightly higher than the other estimates. The updated measurement of the velocity dispersion erased the deviation of S1101 in the L-sigma relation.

The dense environment of galaxy clusters strongly influences the nature of galaxies. Their abundance and diversity is imprinted on the stellar-mass-size plane. Here, we study the cause of the size distribution of a sample of 560 spectroscopic members spanning a wide dynamical range down to 10(8.5) M-circle dot (log(M) - 2) in the massive CLASH cluster MACSJ1206.2-0847 at z = 0.44. We use Subaru SuprimeCam imaging covering the highest-density core out to the infall regions (3 virial radii) to look for cluster-specific effects on a global scale. We also compare our measurements to a compatible large field study in order to span extreme environmental densities. This paper presents the trends we identified for cluster galaxies divided by their colors into star forming and quiescent galaxies and into distinct morphological types (using Sersic index and bulge/disk decompositions). We observed larger sizes for early-type galaxies and smaller sizes for massive late-type galaxies in clusters in comparison to the field. We attribute this to longer quenching timescales of more massive galaxies in the cluster. Our analysis further revealed an increasing importance of recently quenched transition objects ("red disks"), where the correspondence between galaxy morphology and color is out of sync. This is a virialized population with sizes similar to the quiescent, spheroid-dominated population of the cluster center, but with disks still in-tact, and found at higher cluster-centric radii. The mass-size relation of cluster galaxies may therefore be understood as the consequence of a mix of progenitors formed at different quenching epochs. We also investigate the stellar-mass-size relation as a representation of galaxy sizes smoothly decreasing as a function of bulge fraction. We find that at an identical bulge-to-total ratio and identical stellar mass, quiescent galaxies are smaller than star forming galaxies. This is likely because of a fading of the outskirts of the disk, which we saw in comparing sizes of their disk-components. Ram-pressure stripping of the cold gas and other forms of more gradual gas starvation are likely responsible for this observation.

Aims. 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? Methods. We obtained optical spectroscopy of > 400 galaxies in the field of the merging cluster Abell 520. We combine these observations with archival data to obtain 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 ten non-merging clusters at the same redshift from The Arizona Cluster Redshift Survey (ACReS). We split the member galaxies into passive, star forming or recently quenched depending on their spectra. Results. 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 (less than or similar to 0.4 Gyr). Additionally, we report the tentative discovery of an infalling group along the main filament feeding the merger, currently at similar to 2 : 5 Mpc from the merger centre. This group contains a high fraction of star forming galaxies as well as approximately two thirds of all the recently quenched galaxies in our survey.

We took spatially resolved slit FORS2 spectra of 19 cluster galaxies at z=1.4, and 8 additional field galaxies at 1<z<1.2 using the ESO Very Large Telescope. The targets were selected from previous spectroscopic and photometric campaigns. Our spectroscopy was complemented with HST-ACS imaging in the F775W and F850LP filters, which is mandatory to derive the galaxy structural parameters accurately. We analyzed the ionized gas kinematics by extracting rotation curves from the two-dimensional spectra. Taking into account all geometrical, observational, and instrumental effects, we used these rotation curves to derive the intrinsic maximum rotation velocity (Vmax). Vmax was robustly determined for 6 cluster galaxies and 3 field galaxies. Galaxies with sky contamination or insufficient spatial rotation curve extent were not included in our analysis. We compared our sample to the local B-band Tully-Fisher relation (TFR) and the local Velocity-Size relation (VSR), finding that cluster galaxies are on average 1.6 mags brighter and a factor 2-3 smaller. We tentatively divided our cluster galaxies by total mass (i.e., Vmax) to investigate a possible mass dependency in the environmental evolution of galaxies. The average deviation from the local B-band TFR is -0.7 mags for the high-mass subsample. This mild evolution may be driven by younger stellar populations of distant galaxies with respect to their local counterparts, and thus, an increasing luminosity is expected towards higher redshifts. However, the low-mass group is made of 3 highly overluminous galaxies with average TFR offsets of -2.4 mags. This deviation can no longer be explained by the gradual evolution of SP with lookback time and thus, we suspect that we see rather compact galaxies that got an enhancement of star formation during their infall towards the dense regions of the cluster due to interactions with the intracluster medium.

(abridged) We explore the Frontier Fields cluster MACS J0416.1-2403 at z=0.3972 with VIMOS/VLT spectroscopy from the CLASH-VLT survey covering a region which corresponds to almost three virial radii. We measure fluxes of 5 emission lines of 76 cluster members enabling us to unambiguously derive O/H gas metallicities, and also SFRs from Halpha. For intermediate massses we find a similar distribution of cluster and field galaxies in the MZR and mass vs. sSFR diagrams. Bulge-dominated cluster galaxies have on average lower sSFRs and higher O/Hs compared to their disk-dominated counterparts. We use the location of galaxies in the projected velocity vs. position phase-space to separate our cluster sample into a region of objects accreted longer time ago and a region of recently accreted and infalling galaxies. We find a higher fraction of accreted metal-rich galaxies (63%) compared to the fraction of 28% of metal-rich galaxies in the infalling regions. Intermediate mass galaxies falling into the cluster for the first time are found to be in agreement with predictions of the fundamental metallicity relation. In contrast, for already accreted star-forming galaxies of similar masses, we find on average metallicities higher than predicted by the models. This trend is intensified for accreted cluster galaxies of the lowest mass bin, that display metallicities 2-3 times higher than predicted by models with primordial gas inflow. Environmental effects therefore strongly influence gas regulations and control gas metallicities of log(M/Msun)<10.2 (Salpeter IMF) cluster galaxies. We also investigate chemical evolutionary paths of model galaxies with and without inflow of gas showing that strangulation is needed to explain the higher metallicities of accreted cluster galaxies. Our results favor a strangulation scenario in which gas inflow stops for log(M/Msun)<10.2 galaxies when accreted by the cluster.

We present the first, preliminary results from our ongoing survey of galaxies residing in Abell 520 (z=0.2), a cluster in the process of formation at the crossing of three large-scale structure filaments. We use spectroscopy for 682 galaxies, 317 of which reside within the cluster, to search for signs of transformation in the galaxies in this extreme environment. We apply classical definitions of local and global environment to find that both contribute to the quenching of star-formation as measured by the fraction of galaxies with emission lines.