The present study tries to identify the mechanism responsible for the hostility to star formation (SF) found in galaxies of dense environments. Among the several candidate mechanisms, the gas-rich merger of galaxies stands as a plausible option since the realisation that the AGN-feedback, which follows the merger, can deplete the gas and truncate the SF of the resulting spheroid. Our strategy is to look for traces of SF truncation in the elliptical galaxies of Hickson compact groups (HCGs), because these are the ideal environments for mergers to occur. The stellar populations of 22 elliptical galaxies in HCGs and 12 in the field are compared using three different SSP models and two different emission correction procedures. Along the study, an extensive use of the [Mg/Fe] abundance ratio is made, because it contains useful information on the timescale of the SF history of the galaxies. Systematic differences of [Mg/Fe] and [Z/H] between both galaxy subsamples (field and HCGs) suggest that SF truncation events have affected the intermediate-mass galaxies of the HCGs. Our interpretation is that when a field galaxy enters the dense HCG environment it merges with another galaxy and ends up as a passive elliptical with traces of SF truncation.

We present a study of 413 early-type dwarf (dE) galaxies in the Virgo Cluster with SDSS multicolour imaging. Several dE subclasses show systematic differences in shape, clustering properties, and stellar content. We find different colour-magnitude relations for nucleated and non-nucleated dEs, as well as for dE samples populating regions of different densities.

The MAGPOP-ITP is a large observational project of the EU MAGPOP Network. In order to study the star formation history of dwarf galaxies, a total of 60 nights was allocated on the 4 large La Palma telescopes in the framework of an International Time Programme. The programme comprises continuum, Hα and near-infrared imaging and optical spectroscopy of quiescent and star-forming dwarfs in the field and in the Virgo Cluster. All galaxies in the sample are selected to have imaging in the UV (by GALEX) and in the optical (by SDSS), and many have additional data available in the GOLDMine database.

The aim of the programme is to study the star formation of dwarf galaxies in function of their environment and dwarf type. In this contribution, I will focus on the results obtained for dwarf elliptical galaxies (dEs) using long-slit optical spectroscopy obtained with the NOT. We derive mean luminosity-weighted ages and metallicities using Lick indices for 25 dEs.

The dEs show a large spread in both ages and metallicities, but overall they are younger and less metal-rich than normal ellipticals (Es). The [α/Fe] ratios of the dEs are compatible with solar ratios, or are even slightly underabundant, pointing at prolonged star formation histories for dEs.

Based on FORS2-VLT long-slit spectroscopy, the analysis of the central absorption line indices of 9 S0 galaxies in the Fornax Cluster is presented. Central indices correlate with central velocity dispersions (σ0) as observed in ellipticals (E). However, the stellar population properties of these S0s indicates that the observed trends are produced by relative differences in age and α-element abundances and not in metallicity ([Fe/H]) as previous studies have found in E galaxies. The observed scatter in the line indices versus σ0 relations can be partially explained by the rotationally-supported nature of many of these systems. The presence of tighter line indices vs. maximum (circular) rotational velocity (VMAX) relations confirms this statement. It was also confirmed that the dynamical mass is the driving physical property of all these correlations and in our Fornax S0s it has to be estimated assuming rotational support.

Secular evolution theory predicts that spheroidal components are formed thanks to bars that can transport gas to the central regions of the galaxies. This activity would trigger the star formation needed to generate galactic bulges. According to this idea, bars at smaller scales may carry material to the galactic center and feed active galactic nuclei. For the first time, we have carried out a complete kinematical and stellar population analysis of a double-barred galaxy (NGC 357) to determine if this system of two bars is efficient enough to cause that kind of effects. We have measured suitable line-strength indices on high quality spectra to obtain the relative ages and metallicities for the different structural components and thus constrain the star formation history. First results seems to indicate that in the case of NGC 357 the nuclear bar hasn't played an important role in fueling the star formation in the center.

We present preliminary long-slit spectroscopy of a sample of nearby cD galaxies recently observed with the William Herschel and GEMINI North and South Telescopes. So far, we have accumulated data for 27 cDs. More is being observed with the GEMINI telescopes, to create a statistically significant sample. Unresolved stellar populations will be used to investigate the history of when stars formed in these galaxies. Central and spatially resolved line strengths measured from these high signal-to-noise data will be interpreted via population modelling and used to derive luminosity weighted average ages and abundances. Comparison with previous results from other Hubble types of galaxies will highlight relative differences in their evolution.

The spatial distributions of the mean luminosity-weighted stellar age, metallicity, and α/Fe ratio along both photometric axes of two nearby elliptical galaxies have been obtained using Lick index measurements on long slit spectra in order to reconstruct the star formation history in their kinematically distinct subsystems. Lick indexes were compared with those of single-aged stellar population (SSP) models. A population synthesis method was also applied in order to help disentangling the age-metallicity degeneracy. The stars characteristics are associated with their kinematics: they are older and α-enhanced in the not rotating bulge of NGC 1052 and counter rotating core of NGC 7796, while they show a strong spread of α/Fe and age along the rotating disk of NGC 1052 and an outwards radial decreasing of them outside the core of NGC 7796.

We present a detailed study of stellar line indices along the bar region for a sample of six early-type galaxies. We find positive gradients within the bar region in the metal indices in four of the six galaxies, and opposite trends in the other two. These latter two galaxies are classified as SAB and they present exponential bar light profiles. For all the galaxies, we find a positive gradient in the Balmer indices. There is a clear correlation between the position of morphological features inside the bar region with changes in the slope and value of the indices, which indicate, using stellar population analysis, changes in the stellar population. Therefore, it seems that the bar regions show a gradient in both age and metallicity, changing radially to younger and more metal rich populations for all the galaxies except for those two with exponential profiles. This is the first time such an analysis of the stellar populations in bars has been performed. The radial distribution of the indices is related to the star formation history of the bar, understanding these trends will help us to understand how bars are formed and how they evolve.

Recent observations have revealed a class of unusually HI-rich early-type galaxies. By combining observations of their morphology, stellar populations and neutral hydrogen we aim to understand how these galaxies fit into the hierarchical formation paradigm. Here we present the result of our radio and optical observations of a test case galaxy, the E/S0 IC 4200.

We present some preliminary results obtained within the MAGPOP-ITP collaboration for a subsample of four dwarf elliptical galaxies. On the basis of high-resolution, optical spectroscopic data obtained for these galaxies at the WHT, their ages, metallicities and single element abundance ratios have been derived from their line-strength indices and the improved, MILES-based, stellar population model predictions by Vazdekis et al. (in preparation).

We present first results from an HST/ACS imaging survey of stars and star clusters in five nearby spiral galaxies. This contribution concentrates on NGC 1313, a highly distorted late-type barred spiral. We compare the field star and cluster formation histories in our three ACS pointings for this galaxy. In one pointing, both the cluster and field star age distributions show clear evidence for a ramp-up in the star formation rate about 108 years ago.

We present preliminary results from a new wide-field photometric investigation of the globular cluster system of NGC 5128. NGC 5128 is the nearest giant elliptical and thus its globular cluster system serves as prototype for those of this important galaxy type. We have obtained images from IMACS at the Magellan telescope in excellent seeing that allow us to not only resolve globular clusters but derive their structural parameters. This extensive database provides a wealth of data to study the globular clusters in unprecedented detail. We discuss here the resolution of the clusters and their preliminary structural parameters.

Understanding the stellar populations of extragalactic globular cluster (GC) systems and, in particular, determining their ages, provide essential clues to constrain the star formation histories of their host galaxies. We here summarize the most relevant results derived from a detailed, spectroscopic study of 20 GCs in the E0 NGC 1407. We find most GCs are old (~11 Gyr), follow a tight metallicity sequence reaching values slightly above solar, and exhibit mean [α/Fe] ratios of ~0.3 dex. Blue horizontal branch effects are detected for 3 GCs. We also report the existence of two families of metal-rich (MR) GCs, as some of them exhibit significantly larger [Mg/Fe] and [C/Fe] ratios, what might be interpreted in terms of different star formation time-scales. Striking CN overabundances are found over the entire GC metallicity range. In particular, for MR GCs, N increases dramatically while C essentially saturates. This may be interpreted as a consequence of the increasing importance of the CNO cycle with increasing metallicity.

Photometric studies on globular cluster systems in early-type galaxies are widely used to resolve stellar populations in these galaxies. The knowledge of the age and metalicity structure within the globular cluster systems allows to set constraints on the major star formation episodes in the galaxy. Here we present our method of detecting age sub-populations in globular cluster systems based on optical/near-infrared observations and Monte-Carlo simulations. It is based on the determination of the cumulative age distribution and its comparison to simulated globular cluster systems. On various galaxies we will demonstrate the ability of our method to detect age sub-populations and show how we use the derived age structure to find correlations between various galaxy parameters and the formation/evolution of a given galaxy.

We present a star cluster population study in the interacting galaxy system M51 based on HST ACS BV I mosaic images taken by the Hubble Heritage Team to commemorate the HST's 15th anniversary. We have found and classified star clusters in M51 using SExtractor and visual inspection. We have derived the photometry, size, and age of the clusters. It is found that the companion SB0 galaxy NGC 5195 harbors about 50 faint fuzzy clusters and that the age distribution of star clusters appears to be correlated with the epochs of dynamical events in M51 system.

We have recently obtained optical spectra for a large sample of young and intermediate-age star clusters in several nearby galaxies. The main aim of this programme is to carry out a detailed test of photometric and spectroscopic age- and metallicity indicators, but a first inspection of the data has also revealed emission lines in 3 clusters with ages of 30 Myrs or older. We identify these three objects as likely Planetary Nebula (PN) candidates and discuss their properties. Based on the cluster ages, the progenitor stars had initial masses in the range 3 to 7 M⊙, while the PN central stal luminosities and temperatures (estimated from emission line fluxes) are consistent with current masses close to 0.60 M⊙. These objects represent a rare opportunity to study PNe whose progenitor stars are known to be of intermediate masses, although detailed analysis is challenging because of the strong underlying stellar continuum from the cluster stars. Detection of 3 PNe in our sample appears consistent with expectations from stellar evolutionary theory.

We present preliminary results of a wide-field spectroscopic study on star clusters in the spiral galaxy M 33. We derive for 42 star clusters both age and metallicity using the principles of the Bayesian statistic and the Lick indices. We find that M 33 globular clusters in our sample are relatively young (∼8 – 9 Gyr), none of them being as old as the oldest Galactic counterparts. This implies that this galaxy started forming most of its star clusters after the main episode of star formation took place in the big Local Group galaxies (Milky Way, M 31 and LMC), possibly together with the SMC.

Do LSB galaxies have globular clusters? If they do, how do the main features of these systems compare to the ones observed in other galaxies? What are the implications of these findings on the formation of the halo and the star formation history of LSB galaxies? These are the questions we are looking to address with this study.

We present preliminary results of an ACS/HST survey for globular clusters on massive LSB galaxies.

The combination of huge databases of galaxy spectra and advances in evolutionary synthesis models in the past few years has renewed interest in an old question: How to estimate the star formation history of a galaxy out of its integrated spectrum? Fresh approaches to this classical problem are making it possible to extract the best of both worlds, producing exquisite pixel-by-pixel fits to galaxy spectra with state-of-the-art stellar population models while at the same time exploring the fabulous statistics of mega-surveys to derive the star-formation and chemical enrichment histories of different types of galaxies with an unprecedented level of detail. This review covers some of these recent advances, focusing on results for late-type, star-forming galaxies, and outlines some of the issues which will keep us busy in the coming years.

We present integral-field observations of kinematically decoupled components (KDCs) in a sample of 24 Sa galaxies part of the SAURON Survey. We show how the V/σ maps can be used to highlight the presence of the KDC and investigate their stellar populations (i.e. age) to understand their origin (i.e. secular vs hierarchical scenarios). We find that KDCs can be long-lived and are typically well aligned with the galaxies kinematical major axis, supporting mounting evidence that secular evolution becomes important at intermediate redshifts. Dynamically colder ones seem to host younger stellar populations. We also relate these features to the ones found in our sample of 48 elliptical and lenticular galaxies. We find that there is no age vs size relation for these decoupled components in Sa galaxies, suggesting that the dominant factor determining their size is the amount of star formation they have been subject to during their life time.