We present the widest-field resolved stellar map to date of the closest (D ∼ 3.8 Mpc) massive elliptical galaxy NGC 5128 (Centaurus A; Cen A), extending out to a projected galactocentric radius of ∼ 150 kpc. The dataset is part of our ongoing Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) utilizing the Magellan/Megacam imager. We resolve a population of old red giant branch stars down to ∼ 1.5 mag below the tip of the red giant branch, reaching surface brightness limits as low as µ V,0 ∼ 32 mag arcsec −2 . The resulting spatial stellar density map highlights a plethora of previously unknown streams, shells, and satellites, including the first tidally disrupting dwarf around Cen A (CenA-MM-Dw3), which underline its active accretion history. We report 13 previously unknown dwarf satellite candidates, of which 9 are confirmed to be at the distance of Cen A (the remaining 4 are not resolved into stars), with magnitudes in the range M V = −7.2 to −13.0, central surface brightness values of µ V,0 = 25.4−26.9 mag arcsec −2 , and half-light radii of r h = 0.22−2.92 kpc. These values are in line with Local Group dwarfs but also lie at the faint/diffuse end of their distribution; interestingly, CenA-MM-Dw3 has similar properties to the recently discovered ultra-diffuse galaxies in Virgo and Coma. Most of the new dwarfs are fainter than the previously known Cen A satellites. The newly discovered dwarfs and halo substructures are discussed in light of their stellar populations, and they are compared to those discovered by the PAndAS survey of M31.

We present a homogeneous set of stellar atmospheric parameters (T eff , log g, [Fe/H]) for MILES, a new spectral stellar library covering the range λλ 3525-7500 Å at 2.3 Å (FWHM) spectral resolution. The library consists of 985 stars spanning a large range in atmospheric parameters, from super-metal-rich, cool stars to hot, metal-poor stars. The spectral resolution, spectral type coverage and number of stars represent a substantial improvement over previous libraries used in population synthesis models. The atmospheric parameters that we present here are the result of a previous, extensive compilation from the literature. In order to construct a homogeneous data set of atmospheric parameters we have taken the sample of stars of Soubiran, Katz & Cayrel, which has very well determined fundamental parameters, as the standard reference system for our field stars, and have calibrated and bootstrapped the data from other papers against it. The atmospheric parameters for our cluster stars have also been revised and updated according to recent metallicity scales, colour-temperature relations and improved set of isochrones.

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 that are selected from the GALEX Ultraviolet Virgo Cluster Survey (GUViCS) with the purpose of understanding the origin of the red sequence in dense environments. The sample spans a wide range in morphological types (from dwarf ellipticals to Im and BCD) and stellar masses (10 7 M star 10 11.5 M ). We collected multifrequency data covering the whole electromagnetic spectrum for most of the galaxies, including UV, optical, mid-and far-infrared imaging data, as well as optical and HI spectroscopic data. We first identify the different dynamical substructures that compose 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 or as a function of galaxy density. Our analysis indicates that all the most massive galaxies (M star 10 11 M ) are slow rotators and are the dominant galaxies of the different cluster substructures, which are generally associated with a diffuse X-ray emission. They are probably the result of major merging events that occurred at early epochs, as also indicated by their very old stellar populations. Slow rotators of lower stellar mass (10 8.5M star 10 11 M ) are also preferentially located within the different high-density substructures of the cluster. Their position in the velocity space indicates that they are virialised within the cluster; thus, they are Virgo members since its formation. They have been shaped by gravitational perturbations occurring within the infalling groups that later form the cluster (pre-processing). 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.

Using MegaCam at the CFHT, we obtained a deep narrow band Hα+ [NII] wide-field image of NGC 4569 (M90), the brightest late-type galaxy in the Virgo cluster. The image reveals the presence of long tails of diffuse ionized gas, without any associated stellar component extending from the disc of the galaxy up to 80 kpc (projected distance) and 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 ionized gas that is associated with the nucleus that spectroscopic data identify as an outflow. With some assumptions on the 3D distribution of the gas, we use the Hα surface brightness of these extended low-surface brightness features to derive the density and the mass of the gas that has been stripped during the interaction of the galaxy with the intracluster medium. The comparison with ad hoc chemo-spectrophotometric models of galaxy evolution indicates that the mass of the Hα emitting gas in the tail is a large fraction of that of the cold phase that has been stripped from the disc, suggesting that the gas is ionized within the tail during the stripping process. The lack of star-forming regions suggests that mechanisms other than photoionization 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 M ) galaxies located in intermediate-mass ( 10 14 M ) clusters under formation. It also shows that the mass of gas expelled by the nuclear outflow is only ∼1% than that removed during the ram pressure stripping event. Together these results indicate that ram pressure stripping, rather than starvation through nuclear feedback, can be the dominant mechanism that is responsible for the quenching of the star formation activity of galaxies in high density environments.Key words. galaxies: individual: NGC 4569 -galaxies: clusters: general -galaxies: clusters: individual: Virgo -galaxies: evolutiongalaxies: interactions -galaxies: ISM Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canadian-French-Hawaii Telescope (CFHT) which is operated by the

Using deep, high resolution optical imaging from the Next Generation Virgo Cluster Survey we study the properties of nuclear star clusters (NSCs) in a sample of nearly 400 quiescent galaxies in the core of Virgo with stellar masses 10 5 M * /M 10 12 . The nucleation fraction reaches a peak value f n ≈ 90% for M * ≈ 10 9 M galaxies and declines for both higher and lower masses, but nuclei populate galaxies as small as M * ≈ 5 × 10 5 M . Comparison with literature data for nearby groups and clusters shows that at the low-mass end nucleation is more frequent in denser environments. The NSC mass function peaks at M N SC ≈ 7 × 10 5 M , a factor 3-4 times larger than the turnover mass for globular clusters (GCs). We find a nonlinear relation between the stellar masses of NSCs and of their host galaxies, with a mean nucleus-to-galaxy mass ratio that drops to M N SC /M ≈ 3.6 × 10 −3 for M * ≈ 5 × 10 9 M galaxies. Nuclei in both more and less massive galaxies are much more prominent: M N SC ∝ M 0.46 * at the low-mass end, where nuclei are nearly 50% as massive as their hosts. We measure an intrinsic scatter in NSC masses at fixed galaxy stellar mass of 0.4 dex, which we interpret as evidence that the process of NSC growth is significantly stochastic. At low galaxy masses we find a close connection between NSCs and GC systems, including a very similar occupation distribution and comparable total masses. We discuss these results in the context of current dissipative and dissipationless models of NSC formation.

Dwarf galaxies, as the most numerous type of galaxy, offer the potential to study galaxy formation and evolution in detail in the nearby universe. Although they seem to be simple systems at first view, they remain poorly understood. In an attempt to alleviate this situation, the MAGPOP EU Research and Training Network embarked on a study of dwarf galaxies named MAGPOP‐ITP. In this paper, we present the analysis of a sample of 24 dwarf elliptical galaxies (dEs) in the Virgo cluster and in the field, using optical long‐slit spectroscopy. We examine their stellar populations in combination with their light distribution and environment. We confirm and strengthen previous results that dEs are, on average, younger and more metal‐poor than normal elliptical galaxies, and that their [α/Fe] abundance ratios scatter around solar. This is in accordance with the downsizing picture of galaxy formation where mass is the main driver for the star formation history. We also find new correlations between the luminosity‐weighted mean age, the large‐scale asymmetry, and the projected Virgocentric distance. We find that environment plays an important role in the termination of the star formation activity by ram‐pressure stripping of the gas in short time‐scales, and in the transformation of discy dwarfs to more spheroidal objects by harassment over longer time‐scales. This points towards a continuing infalling scenario for the evolution of dEs.

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band Hα+ [NII] imaging survey carried out with MegaCam at the Canada-France-Hawaii Telescope. During pilot observations taken in the spring of 2016 we observed NGC 4330, an intermediate mass (M * 10 9.8 M ) edge-on star forming spiral currently falling into the core of the Virgo cluster. While previous Hα observations showed a clumpy complex of ionised gas knots outside the galaxy disc, new deep observations revealed a low surface brightness ∼ 10 kpc tail exhibiting a peculiar filamentary structure. The filaments are remarkably parallel to one another and clearly indicate the direction of motion of the galaxy in the Virgo potential. Motivated by the detection of these features which indicate 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 were stripped ∼ 500 Myr ago, while the stripping reached the inner 5 kpc from the centre in the last 100 Myr. Regions at even smaller radii are currently still forming stars fueled by the presence of HI and H 2 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.

The Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) is constructing a wide-field map of the resolved stellar populations in the extended halos of these two nearby, prominent galaxies. We present new Magellan/Megacam imaging of a ∼ 3 deg 2 area around Centaurus A (Cen A), which filled in much of our coverage to its south, leaving a nearly complete halo map out to a projected radius of ∼150 kpc and allowing us to identify two new resolved dwarf galaxies. We have additionally obtained deep Hubble Space Telescope (HST) optical imaging of eleven out of the thirteen candidate dwarf galaxies identified around Cen A and presented in Crnojević et al. (2016b): seven are confirmed to be satellites of Cen A, while four are found to be background galaxies. We derive accurate distances, structural parameters, luminosities and photometric metallicities for the seven candidates confirmed by our HST/ACS imaging. We further study the stellar population along the ∼60 kpc long (in projection) stream associated with Dw3, which likely had an initial brightness of M V ∼−15 and shows evidence for a metallicity gradient along its length. Using the total sample of eleven dwarf satellites discovered by the PISCeS survey, as well as thirteen brighter previously known satellites of Cen A, we present a revised galaxy luminosity function for the Cen A group down to a limiting magnitude of M V ∼ −8, which has a slope of −1.14 ± 0.17, comparable to that seen in the Local Group and in other nearby groups of galaxies.