We have derived radial sky-subtracted surface brightness profiles of a sample of 42 face-on nearby early-type spiral galaxies, classified as unbarred, from SDSS data as well as our own observations (INT/WFC) at La Palma. A key objective was to derive the fraction of truncated profiles. We find that only a small minority 7% of the galaxies are obviously truncated within the limits of the measured surface brightness range, while some 20% show exponential disc profiles but with a shallower inner portion near the centre: classical “Freeman Type II” profiles (Freeman, 197). Half of the discs show a single unbroken exponential (“type I”) brightness profile with no evidence of truncation out to the edge of detectability, while the remainder show “antitruncations”: external profiles less steep than those of the internal disc (Type III). A general profile classification scheme based on these and other recent related measurements is presented, and will be of use in probing disc formation scenarios.

We have compared simple stellar populations (SSPs) generated with different population synthesis tools: BC03, Vazdekis and Pégase.HR and different stellar libraries: ELODIE3.1, SteLib and MILES. We find that BC03/SteLib SSPs are biased toward solar metallicity, however Pégase.HR/ELODIE3.1 and Vazdekis/MILES are extremely consistent. The extensive coverage of the space of atmospheric parameters in the large stellar libraries allows precise synthesis for a large range of ages (0.1 .. 10 Gyr) and metallicities (−2 .. +0.4 dex) limited by the quality of the determination of stellar parameters (temperature scale of the giants).

We present a progress report of a project to study the quantitative star formation history (SFH) in different parts of the Small Magellanic Cloud (SMC). We use the information in [(B-R), R] color-magnitude diagrams (CMDs), which reach down to the oldest main-sequence turnoffs and allow us to retrieve the SFH in detail. We show the first results of the SFH in a SMC field located in the Southern direction (at ∼1 kpc from the SMC center). This field is particularly interesting because in spite of being located in a place in which the HI column density is very low, it still presents a recent enhancement of star formation.

Recent calculations of evolutionary tracks of TP-AGB stars of different mass and metallicity by Marigo et al. (2007) have been incorporated in the Bruzual & Charlot evolutionary population synthesis models. The mass of the stellar population in HUDF galaxies at z from 1 to 3 determined from fits to the spectro-photometric data of these galaxies is 50 to 80% lower than the mass determined from the BC03 models. The ages inferred for these populations are, with exceptions, 40 to 60% of the BC03 estimates.

The study of stellar populations is a discipline that is highly dependent on both imaging and spectroscopy. I discuss techniques in different regimes of resolving power: broadband imaging (R∼4), intermediate band imaging (R∼16, 64), narrowband spectral imaging (R∼256, 1024, 4096). In recent years, we have seen major advances in broadband all-sky surveys that are set to continue across optical and IR bands, with the added benefit of the time domain, higher sensitivity, and improved photometric accuracy. Tunable filters and integral field spectrographs are poised to make further inroads into intermediate and narrowband imaging studies of stellar populations. Further advances will come from AO-assisted imaging and imaging spectroscopy, although photometric accuracy will be challenging. Integral field spectroscopy will continue to have a major impact on future stellar population studies, extending into the near infrared once the OH suppression problem is finally resolved. A sky rendered dark will allow a host of new ideas to be explored, and old ideas to be revisited.

We present line-strength maps of a sample of 18 late-type spirals. The data have been taken using SAURON at the WHT. Apart from the maps, we present the central line indices, and estimate the star formation time-scale. In an exponentially declining SFR scenario, we find a trend between the time-scale τ and the velocity dispersion: more massive galaxies show shorter burst durations. This result is in agreement with the analysis of Hα emission in galaxies. A detailed study on these data will be published by Ganda et al. (2007).

IAC-pop is a code designed to solve the star formation history (SFH) of a complex stellar population system, like a galaxy, from the analysis of the color-magnitude diagram (CMD). It uses a genetic algorithm to minimize a χ2 merit function comparing the stellar distribution of an observed CMD and the stellar distributions of CMDs arising from linear combination of simple synthetic populations. To this purpose, IAC-star is used to compute a single seminal synthetic CMD from which the simple populations and their corresponding CMD stellar distributions are extracted.

In the current version, IAC-pop provides two different estimates of the errors in the SFH. It is offered for free use and can be downloaded from the site www.iac.es/iac-pop.html.

Only stellar atmosphere models that span a wide range of optical depth can allow a correct treatment of radiative transfer at all the frequencies of the spectrum.

By using synthetic integrated spectral energy distribution (ISED) of open clusters and a new evolutionary scenario involving interactive binaries, the theoretical model of simple stellar population (SSP) models are tested. Blue stragglers stars are commonly present in open clusters, which are usually around 2 magnitudes brighter and much bluer than the MS turn-off of the cluster, and they certainly belong to the same population as the host cluster. Considering the cluster as the nearest counterpart the concept of SSP, inclusion of such stars may have significant consequences on the integrated of properties of the population. We are showing in the present work that if one is to fit the real stellar population using the classical model based only on single star evolution theory, large errors in either age or metallicity (or both) can be made. The new theoretical SSP incorporated with interactive binaries can explain part of the difference between classical SSP model and synthetic ISED built up with open clusters. This suggests that the formation of blue stragglers in real clusters is more complicated as usually assumed in binary stellar population synthesis.

In this poster we present the analysis of the CMD of M67 (proposed in the Stellar Population Challenge) performed with VO applications. We found that, although the VO environment is still not ready to perform a complete analysis, its use provides highly useful additional information for the analysis. Thanks to the current VO framework, we are able to identify stars in the provided CMD that are not suitable for isochrone fitting. Additionally, we can complete our knowledge of this cluster extending the analysis to IR colors, which were not provided in the original data but that are available thanks to the VO. On the negative side, we find it difficult to access theoretical data from VO applications, so, currently, it is not possible to perform completely the analysis of the cluster inside the VO framework. However it is expected that the situation will improve in a near future.

We present the effects due to alpha-element enhancement on surface brightness fluctuation magnitudes and broad-band colors in order to investigate the calibration zero-point. We study these effects at ages covering 0.1 to 13 Gyr and metallicities of Z=0.0003 to 0.04 using the Teramo group's isochrones, BaSTI. Our preliminary results indicate that alpha-enhanced models are needed to match massive red galaxies while solar-scaled models are fine for dwarf blue galaxies to reproduce their independently estimated ages and metallicities.

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.

We present a cautionary study characterizing the influence of non-solar abundance ratios on Hδ derived ages in the integrated light of early-type galaxies. We measure Hδ using a variety of index measurements designed to assess contamination from CN molecular lines in and around the Hδ feature. We propose that neighboring CN lines have a strong effect on continuum levels and the Hδ feature itself, thereby leading to a difficulty in designing an accurate Hδ index definition in populations with C andor N non-solar abundance ratios with population synthesis models that do not account for such variations.

We have derived chemical abundances for Ca, Ti, Si, Mg, O, Na, Al, Ni, Co and Cr for a sample of stars with peculiar kinematics and probable origin near the bulge. Our sample stars are in the metallicity range = −0.8 ≤ [Fe/H] ≤ +0.6 dex, and have small pericentric distances, Rp ≤ 3.5 kpc, small scale height, with Zmax < 0.16 kpc, and old ages, 9 to 11 Gyr. We have found that the abundance distributions of O, Mg and Al lie between bulge and both thin and thick disks distributions, i. e., with an enhanced pattern relative to thin and thick disk stars, and an underabundant behavior compared to bulge stars. [Na/Fe] ratios ovelarp the bulge distribution in the metal-poor tail, and show similar values compared to thin and thick disk stars for the super-solar metallicity range. Ca, Ti and Si values are similar to those of the thick disk stars in the metal-poor range, while an underabundant behavior is seen relative to thin disk stars for metallicities [Fe/H] > +0.3 dex. Compared to bulge stars, such elements are deficient in our sample stas. For the iron-peak elements Cr and Ni we have found a slightly overabundant behavior relative to both thin and thick disks distributions in the metal-poor range, and a smooth decreasing trend for [Cr/Fe] for stars in the supersolar regime. [Co/Fe] ratios track the solar value in the metal-poor range, and show an underabundant behavior relative do thin disk stars for metallicities [Fe/H] > 0.0 dex.

We analyse the star-forming (SF) properties of the two brightest galaxies in the IC 65 group of galaxies and that of the four newly detected dwarf galaxies in the area of the group. The dIrr galaxies around the IC 65 contain a number of HII regions which show a range of stellar ages, and provide an evidence of propagating SF. The two brightest group galaxies show SF rates of ∼ 1 − 2 M⊙ yr−1, and can fuel the current SF level for about the next 3 – 7 Gyr.

We present extensive photometric and spectroscopic study to give a new insight in the bulge stellar population. Super-solar α/Fe and its constant value along the radial profile, in most of the galaxies, suggest that the star formation in these objects has been fast and occurred at the same time in the whole bulge.

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.

Surface Brightness Fluctuations (SBF) are an useful distance indicator of gas-free galaxies as far as 100-150 Mpc with an accuracy of 5–10%. Recent applications have proved that the SBF technique is also a powerful tool to analyze the stellar content of elliptical-like galaxies by means of data/models comparison. Here we present a comprehensive study of the method on the base of a careful analysis of SBF models and a set of accurate multibands SBF measures obtained with HST.

We have applied the Image Subtraction to B,V time-series photometry of four globular clusters of the Fornax dwarf spheoridal galaxy, which were observed with the 2.2m ESO-MPI, the 6.5m Magellan/Clay, the 4m CTIO/Blanco telescopes and the WFPC2 on board of HST. We have identified RR Lyrae stars and obtained well sampled light curves for the clusters' variables. From the periods and pulsation properties of their RR Lyrae stars Fornax globular clusters seem to be of Oosterhoff intermediate type.

Simulations of the chemical enrichment histories of ten Local Group (LG) dwarf galaxies are presented, employing empirically-derived star formation histories (SFHs), a rich network of isotopic and elemental nucleosynthetic yields, and a range of prescriptions for supernova (SN)-driven outflows. Our main conclusions are that (i) neutron-capture element patterns (particularly that of Ba/Y) suggest a strong contribution from low- and intermediate-mass stars (LIMS), (ii) neutron star mergers may play a relatively larger role in the nucleosynthesis of dwarfs, (iii) SN feedback alone can explain the observed gas fraction in dwarf irregulars (dIrrs), but dwarf spheroidals (dSphs) require almost all their gas to be removed via ram pressure and/or tidal stripping, (iv) the predicted heavy Mg isotope enhancements in the interstellar medium (ISM) of dwarfs may provide an alternate solution to claims of a varying fine structure (v) the gas lost from dwarfs have O,Si/C abundances in broad agreement with intergalactic medium abundances at redshifts 2<z<4, and (vi) the chemical properties of dSphs are well-matched by preventing galactic winds from re-accreting, whilst those of dIrrs are better-matched by incorporating metallicity-dependent cooling and re-accretion of hot winds. Finally, doubts are cast upon a claimed association between LG dSph UMaII and HVC Complex A.