We study the interplay between stellar population of the Brightest Cluster Galaxies (BCG) and cluster global properties. We use X-ray properties from Chandra, ROSAT and ASCA observations and BCGs spectra from SDSS-DR6. Using STARLIGHT we determined the star formation history of the BCGs and look for relations with the intra-cluster gas properties. Our first results show no correlation between the recent star formation with x-ray temperature and dynamic state. An important star formation is happening in cool-core Cluster. This new stellar population has low metallicity, pointing to an external source of cold gas to form stars.

Large optical surveys provide an unprecedsCeented census of galaxies in the local Universe, forming an invaluable framework into which more detailed studies of objects can be placed. But how useful are optical surveys for understanding the co-evolution of black holes and galaxies, given their limited wavelength coverage, selection criteria, and depth? Here we present work-in-progress comparing optical and mid-IR diagnostics of three “unusual” low-z populations (luminous Seyferts, dusty Balmer-strong AGN, ULIRGs) with a set of ordinary star-forming galaxies from the SDSS. We address the questions “how well do the mid-IR and optical diagnostics of star formation and AGN strength agree?” and “to what extent do optical surveys allow us to include extreme, dusty, morphologically disturbed galaxies in our ‘complete’ census of BH-galaxy co-evolution?

The major challenge in studying QSO host galaxies is to remove the QSO contribution, which often outshines the whole system. Our group has acquired the technical ability to handle such data, for images and slit spectroscopy, as well as integral field spectroscopy. We review here the major techniques developed by our team, and their latest applications. We are open for collaboration with other teams to spread the use of these powerful techniques.

We present a study of star clusters in the interacting galaxy M51 using a star cluster catalog that includes about 3600 star clusters with mF555W < 23 mag, compiled by Hwang & Lee (2008). Combined with mF336W-band imaging data taken with the Hubble Space Telescope (HST)'s WFPC2 camera, we have derived the ages and masses of star clusters in M51 using theoretical population synthesis models. The cluster age distribution displays multiple peaks that correspond to the epochs of dynamical encounters predicted by theoretical model studies and the cluster-formation rate appears to increase around the same epochs.

In this brief review I summarise recent progress in the area of stellar dynamics, focusing on the dynamics of bound, self-gravitating stellar associations in isolation and (approximate) equilibrium. The basics of stellar dynamics are first outlined and the importance of stellar evolution is stressed. Subsequently, I argue that the evolution of anisotropic clusters of stars still holds solutions to current outstanding problems, such as the dynamics of galactic nuclei. I take a more personal standpoint when discussing the role of stellar evolution in the dynamics on relaxation timescales and draw from several recent models to underscore that a major step forward has been made in coupling stellar evolution and dynamics. I then briefly visit the issue of multiple stars and highlight some as yet unsolved problems.

We present the results of a multiwavelength campaign searching for young objects in the intragroup medium of seven compact groups of galaxies: HCG 2, 7, 22, 23, 92, 100 and NGC 92. We used Fabry-Perot velocity fields and rotation curves together with GALEX NUV and FUV images, optical R-band and HI maps to evaluate the stage of interaction of each group. We conclude that groups (i) HCG 7 and HCG 23 are in an early stage of interaction, (ii) HCG 2 and HCG 22 are mildly interacting, and (iii) HCG 92, HCG 100 and NGC 92 are in a late stage of evolution. Evolved groups have a population of young objects in their intragroup medium while no such population is found within the less evolved groups. We also report the discovery of a tidal dwarf galaxy candidate in the tail of NGC 92. These three groups, besides containing galaxies which have peculiar velocity fields, also show extended HI tails. Our results indicate that the advanced stage of evolution of a group together with the presence of intragroup HI clouds may lead to star formation in the intragroup medium.

Light elements are important tracers of the internal stellar structure and kinematics. Li and Be are both burned in the stellar interiors but Be requires much higher temperatures and thus we can expect to measure Be abundances in stars which have no detectable Li in their atmospheres. The study of these elements can give us information about processes related to the angular momentum history of these stars, since rotation and angular momentum loss are important mechanisms responsible for the depletion of light elements. Additionally, if pollution has played an important role in determining the high-metal content of planet host stars, we would expect to find a similar or even higher increase in the Li and Be contents. We present Be and Li abundances in a sample of 69 stars with planets and 31 stars without known planetary companion, spanning a large range of effective temperatures.

We present a chemical analysis of seven red giants in the open cluster NGC 3114. Our main goal is to investigate the chemical composition of this cluster, which is not yet available in the literature. We employed the FEROS spectrograph on the ESO 2.2m telescope. Atmospheric parameters and metallicity were derived from the measured equivalent widths of several iron lines using the spectral code moog and Kurucz model atmospheres. We obtained the abundances of O, Al, Ca, Mg, Si, Ti, Ni, Cr, Sc, Y, Zr, La, Ce and Nd by measuring the equivalent widths of the absorption lines of these elements. A mean metallicity of [Fe/H] = 0.05 ± 0.13 relative to the Sun was determined from the data of the red-giant members. This result is in good agreement with the Galactic-disk radial distribution of iron traced by open clusters. We did not find any intrinsic star-to-star scatter in the [element/Fe] ratios for the stars in this cluster. We compare our results with investigations of other open clusters. An age of 8.2 Gyr is derived from isochrone fits.

We present a measurement of the rate of high-z Type Ia supernovae (SNe Ia) using multi-epoch observations of Subaru/XMM-Newton Deep Field (SXDF) with Suprime-Cam on the Subaru Telescope. Although SNe Ia are regarded as a standard candle, progenitor systems of SNe Ia have not been resolved yet. One of the key parameters to show the progenitor systems by observations is the delay time distribution between the binary system formation and subsequent SN explosion. Recently, a wide range of delay time is studied by SN Ia rates compared with an assumed cosmic star formation history. If SNe Ia with short delay time are dominant, the cosmic SN Ia rate evolution should closely trace that of the cosmic star formation. In order to detect a lot of high-z SNe Ia and measure SN Ia rates, we repeatedly carried out wide and deep imaging observations in the í-band with Suprime-Cam in 2002 (FoV~1 deg2, mi < 25.5 mag). We obtained detailed light curves of the variable objects, and 50 objects are classified as SNe Ia using the light curve fitting method at the redshift range of 0.2 < z < 1.3. In order to check the completeness and contamination of the light curve classification method, we performed Monte Carlo simulations and generated ~100,000 light curves of SNe Ia and II from templates. The control time and detection efficiency of the SN survey are also calculated using the artificial light curves. We derived an increasing trend of rates at around z ~ 1.2. Our results are almost consistent with other SN Ia rate results from low-z to high-z. Our results are the first results of high-z SN Ia rates with large statistics using light curves obtained by ground based telescopes, and give us visions of the SN rate studies for the future.

Eight new black hole masses have been derived from a recent reverberation-mapping experiment carried out at Lick Observatory. The masses lie in the range ~ 106–107M⊙ and will allow us to extend the low end of AGN scaling relationships by a factor of ~10.

Recent observations of tight correlations between supermassive black hole masses and the properties of their host galaxies demonstrate that black holes and bulges are co-eval and have motivated theoretical models in which feedback from AGN activity regulates the black hole and host galaxy evolution. Combining simulations, analytic models, and recent observations, answers to a number of questions are starting to take shape: how do AGN get triggered? How long do they live? What are typical light curves and what sets them? Is feedback necessary and/or sufficient to regulate BH growth? What effects does that feedback have on the host galaxy? On the host halo? All of this also highlights questions that remain wide open: how does gas get from a few pc to the AGN? What are the actual microphysical mechanisms of feedback? What is the tradeoff between stellar and AGN feedback? And, if there are different “modes” of feedback, where/when are each important?

The formation of the first stars out of metal-free gas appears to result in stars at least an order of magnitude more massive than in the present-day case. We here consider what controls the transition from a primordial to a modern initial mass function. We study the influence of low levels of metal enrichment and different initial conditions on the cooling and collapse of initially ionized gas in small protogalactic halos using three-dimensional, smoothed particle hydrodynamics simulations. We argue that fragmentation at moderate density depends on the initial conditions for star formation more than on the metal abundances present.

The study of chemical abundances in stars with planets is an important ingredient for the models of formation and evolution of planetary systems. In order to determine accurate abundances, it is crucial to have a reliable set of atmospheric parameters. In this work, we describe the homogeneous determination of effective temperatures, surface gravities and iron abundances for a large sample of stars with planets as well as a control sample of stars without giant planets. Our results indicate that the metallicity distribution of the stars with planets is more metal rich by ~0.13 dex than the control sample stars.

The main goal of this work is to explore the abundance patterns of the very metal-poor stars ([Fe/H]<−2.0) observed by the HERES (Hamburg ESO R-process Enhanced Star - Christlieb et al. 2004) survey. This type of study allows the analysis of the correlations among chemical elements, and place some constraints on the operation of the neutron-capture (r and s) processes in the early Galaxy. This approach makes use of statistical tools, such as agglomerative nesting, which can identify the formation of natural groups based on relations among elemental abundances (e.g. [C/Fe], [Sr/Fe], [Ba/Fe], and [Eu/Fe]), and can also be used in a series of “large-sample like” studies.

This study provides a comprehensive analysis of a sample of 326 metal-poor stars, and introduces two new subclasses (r-0 and s-I) for metal-poor stars with determined abundances of neutron-capture elements, aiming to standardize the nomenclature for those objects and, by reproducing previous results, confirms the validity of the statistical method used.

NGC 3603 is one of the most massive, compact young star clusters in the Milky Way. The cluster has an age of only about 1 Myr and is embedded in a giant molecular cloud with ongoing star formation. We have analyzed deep imaging data obtained with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. We have obtained two epochs separated by 10 years, from which we derived proper motions which we used to determine cluster membership. After the removal of field stars, the resulting color–magnitude diagram shows a main sequence in addition to another clear sequence of pre-main-sequence stars. The cluster shows pronounced mass segregation and appears to have a very short crossing timescale. Our photometric, astrometric and kinematic data help us to evaluate the dissolution timescale of NGC 3603 and whether the mass segregation is likely to be primordial or evolutionary.

Early abundance measurements established that stars known to host giant planets are metal rich compared to the Sun. More extensive abundance measurements then showed that giant planet hosts are metal rich compared to the parent sample in planet searches. Stars spanning a range of convection zone depths all show the same metallicity effect, ruling out significant abundance enhancements due to selective accretion. Most known planets migrated inwards from the snow line, but subsamples closer to and further from the star have similar iron abundances, so the stopping point of migration does not depend on metallicity. Stars recently discovered to host Neptune mass planets may be metal poor compared to the Sun, particularly if one focusses on stars that do not also host higher mass planets. This would be consistent with core-accretion models of planet formation. Before drawing physical conclusions, it will be necessary to check for metallicity bias in the subsample of stars around which Neptune mass planets could have been found. M dwarf abundances are currently too uncertain to relate planet frequency and host star metallicity, due mainly to missing or incorrect molecular line data.

We present the stellar parameters and lithium abundance for 23 stars of the young stellar association AB Doradus, determined by photometry and spectroscopy. The photometric data was obtained at OPD/LNA and/or from the literature and the spectroscopic data was obtained at La silla/ESO and at OPD/LNA. The parameters were determined using photometric calibrations, line ratios, curves of growth and spectral synthesis. Our results confirm that the selected stars are probably association members, showing an uniform metallicity and lithium depletion consistent with 50 Myears

Establishing or ruling out, either through solid mass measurements or upper limits, the presence of intermediate-mass black holes (IMBHs; with masses of 102 − 105 M⊙) at the centers of star clusters would profoundly impact our understanding of problems ranging from the formation and long-term dynamical evolution of stellar systems, to the nature of the seeds and the growth mechanisms of supermassive black holes. While there are sound theoretical arguments both for and against their presence in today's clusters, observational studies have so far not yielded truly conclusive IMBH detections nor upper limits. We argue that the most promising approach to solving this issue is provided by the combination of measurements of the proper motions of stars at the centers of Galactic globular clusters and dynamical models able to take full advantage of this type of data set. We present a program based on HST observations and recently developed tools for dynamical analysis designed to do just that.

Cosmological simulations describing both the evolution of supermassive black holes and their host galaxies were performed by using the tree PM-SPH code GADGET-2 (Springel 2005). Physical mechanisms affecting the dynamics and the physical conditions of the gas (ionization and cooling processes, local heating by stars, injection of mechanical energy by supernovae, chemical enrichment) were introduced in the present version of the code (Filloux 2009). Black holes in a state of accretion (AGNs) also inject mechanical energy in the surrounding medium, contributing for quenching the star formation activity. In all simulations a ΛCDM cosmology was adopted (h = 0.7, ΩΛ=0.7, Ωm=0.3, Ωb=0.046 and σ8=0.9). Simulations were performed in a volume with a side of 50h−1 Mpc, starting at z = 50 and through the present time (z = 0). For low and intermediate resolution runs, the initial gas mass particles are respectively 5.35× 108M⊙ and 3.09×108M⊙. Black holes (BHs) are represented by collisionless particles and seeds of 100 M⊙ were introduced in density peaks at z = 15, growing either by accretion or coalescence. The accretion rate from the “disk mode” is based on a turbulent viscous thin disk model whereas in the “spherical mode” the rate is given by the Bondi–Hoyle formula. When accreting matter, jets, modeled by conical regions perpendicular to the disk plane, inject kinetic energy into the surrounding medium. Two models were tested: in the first, the injected energy rate is about 10% of the gravitational energy rate released in the accretion process while in the second, the injected energy rate is based on the Blandford & Znajek (1977) mechanism. All simulations give, at z = 0, similar black hole mass function but they overestimate slightly the BH density for masses above ~ 108M⊙. The resulting BH density in this mass range is affected by feedback processes since they control the amount of gas available for accretion. The present simulations are not able to produce very massive BHs (~109M⊙) at z ~ 6. However the evolution of the BH mass density derived from our simulations are in quite good agreement with that derived from the QSO luminosity function. This indicates that our simulations reproduce quite well the average accretion rate history of BHs. Correlations between the BH mass and properties of the host galaxy (velocity dispersion for bulge systems or the stellar mass or the dark halo mass) are also well reproduced. In conclusion, these exploratory simulations reproduce the data at z = 0 quite well. However, the present adopted recipe for the accretion rate in the “disk mode” seems to be inefficient to produce massive BHs as early as z ~ 6. Higher resolution simulations including a new approach for modeling the “disk mode” are presently under way and that particular difficulty is expected to be solved.