Stellar clusters are important for astrophysics in many ways, for instance as optimal tracers of the Galactic populations to which they belong or as one of the best test bench for stellar evolutionary models. Gaia DR1, with TGAS, is just skimming the wealth of exquisite information we are expecting from the more advanced catalogues, but already offers good opportunities and indicates the vast potentialities. Gaia results can be efficiently complemented by ground-based data, in particular by large spectroscopic and photometric surveys. Examples of some scientific results of the Gaia-ESO survey are presented, as a teaser for what will be possible once advanced Gaia releases and ground-based data will be combined.

Globular clusters (GCs) are known to have a very small amount of or no dark matter (DM). Even if GCs are formed in individual DM halos, they must have lost the majority of the DM through dynamical processes such as mass segregation or tidal stripping. Using Fokker-Planck (FP) calculations, we investigate the dynamical evolution of three Galactic GCs with an assumption that they were formed in mini DM halos. We trace the amount of DM of 47 Tuc, NGC 1851, and M 15, which are a ‘disk/bulge’ cluster, an ‘old halo’ cluster, and a ‘young halo’ cluster, respectively. We find that these three GCs must have initially had insignificant amounts of DM, less than 10 percent of the initial stellar mass of each cluster.

One of the most important results in the study of Globular Clusters (GC) has been the discovery of bimodality in the broad-band colors of many systems. Observations of the Milky Way, M31 and Centaurus A strongly suggest this is a bi-modality in metallicity. One method of constraining, and perhaps better understanding the observed bimodality of GCs is to use semi-analytic models (SAMs) to test both the galaxy and GC formation scenarios. We present the results of a study to test whether SAMs can accurately reproduce the physical characteristics of both the parent galaxy (including luminosity, mass and metallicity) and GC populations. The focus of the work is to test whether the SAMs are capable of reproducing the observed properties of spiral galaxies, in particular the Milky Way and M31, and what, if any, constraints this may place on the formation scenarios of GCs. Among the results are indications that bimodality may be directly connected with reionization at z ~ 7–8.

We have derived Mn abundances for more than 200 stars in nineteen globular clusters. In addition, Mn abundance determinations have been made for a comparable number of halo field stars possessing an overlapping range of metallicities and stellar parameters. The primary data set was comprised of high resolution spectra previously-acquired at the McDonald, Lick and Keck Observatories. Additional data were obtained from several other investigators. Data were analyzed using synthetic spectra of the 6000 Å Mn I triplet. Hyperfine structure parameters were included in the synthetic spectra computations. Our analysis shows that over the metallicity range $-0.7>[Fe/H]-2.7$ field stars have a mean relative abundance of $<[Mn/Fe]>=-0.36$ identical to that of the nineteen globular clusters $<[Mn/Fe]>=-0.36$. Our Mn abundance results viewed in conjunction with the globular cluster Cu abundances of Simmerer et al. (2003) suggest the following possibilities: one, the production of these elements is highly metallicity-dependent or two, these elements were manufactured in the Galactic halo prior to formation of present-day globular clusters.

Despite its importance, the Galactic Bulge and its globular cluster (GC) system in particular, remain relatively unexplored due to high foreground extinction and severely crowded field populations. The new generation of high resolution IR spectrographs opens new and unique perspectives to obtain detailed abundances in the Bulge field and GCs. Using the NIRSPEC spectrograph at Keck II, high resolution, echelle spectra in the range 1.5–1.8 micron of bright giants in the Baade's window and other fields closer to the Galactic center as well as in a sample of 10 Bulge GCs have been obtained. We present the results of our abundance analysis of Fe, Al, 12C, 13C, O, and other α-elements, by using full spectral synthesis techniques.