In the context of hierarchical galaxy assembly, globular clusters and dwarf galaxies are indispensable probes of the formation of our Milky Way. M22 is a stellar system with chemical abundances reminiscent of an accreted dwarf galaxy such as ω Centauri but disc-like kinematics suggesting a Milky Way origin. Curiously, M22 contains a population of stars enhanced in slow neutron-capture (s-)process elements due to pollution from low-mass AGB stars. Recently, the original in-situ population stars of the Milky Way disc has been revealed to be enhanced in s-process elements. This provides a tantalizing link between the in-situ Milky Way population and the formation of M22. This talk discussed how recent high-precision chemical abundance measurements suggest that M22 may be coeval with this in-situ component, and what the formation mechanisms of this s-process population can tell us about the chemical evolution of our Galaxy before the establishment of the disc.

Observations of stellar chemical compositions enable us to identify connections between globular clusters and stellar populations in the Milky Way. In particular, chemical abundance ratios provide detailed insight into the chemical enrichment histories of star clusters and the field populations. For some elements, there are striking differences between field and cluster stars which reflect different nucleosynthetic processes and/or chemical evolution. The goal of this talk was to provide an overview of similarities and differences in chemical compositions between globular clusters and the Milky Way as well as highlighting a few areas for further examination.

Spectroscopy and photometry have revealed existence, complexity and properties of the multiple stellar populations (mPOPs) hosted in Galactic globular clusters. However, the conundrum of the formation and evolution of mPOPs is far from being completely exploited: the available pieces of information seem not enough to shed light on these topics. Astrometry, and in particular high-precision proper motions, can provide us the sought-after answers about how mPOPs formed and have evolved in these ancient stellar systems. In the following, I present a brief overview of the observational results on the internal kinematics of the mPOPs in some GCs thanks to Hubble Space Telescope high-precision proper motions.

I review the methods, mostly developed in the last decade, that are commonly used to identify and characterize multiple populations (MPs) in Globular Clusters (GCs) based on photometry. I summarize the results from the recent surveys of MPs with the Hubble Space Telescope (HST) and ground-based facilities and provide a list of the main properties of MPs as inferred from these studies.

I present the latest results from our group about the multiple stellar populations in the old Milky Way globular clusters (GCs) and in the young systems both in the Magellanic Clouds and in the Milky Way. For the ancient GCs in our Galaxy I summarize the chemical properties of the stellar populations as observed on the chromosome map. Both Type I and Type II GCs are discussed. For the youngest clusters I will briefly report our latest spectroscopic analysis on the Large Magellanic Cloud cluster NGC 1818 and the Galactic open cluster M 11, which supports the co-existence of stellar populations with different rotation rates.

We present results of our studies for a sample of Galactic globular star clusters with the aim of deriving relative proper motions. We used CCD archival data observed with Wide Field Imager (WFI) mounted on ESO 2.2 m telescope at La Silla, Chile. Astrometric software designed by Anderson et al. is used to derive relative proper motions. The vector point diagrams show clear separation of field stars from the cluster stars. We used proper motions to determine membership probabilities and to produce color-magnitude diagrams with most probable cluster member stars. Our membership catalogue can be used to study the membership status of the peculiar stars including various variables reported in the literature.

This is a “biased” review because I will show recent evidence on the contribution of globular clusters (GCs) to the halo of our Galaxy seen through the lens of the new paradigm of multiple populations in GCs. I will show a few examples where the chemistry of multiple populations helps to answer hot questions including whether and how much GCs did contribute to the halo population, if we have evidence of the GCs-halo link, what are the strengths and weak points concerning this contribution.

We present early results from a detailed analysis of the BSS population in Galactic GCs based on HST data. Using proper motion cleaning of the color-magnitude diagrams we construct a large catalog of BSSs and study some population properties. Stellar evolutionary models are used to find stellar mass and age estimates for the BSS populations in order to establish constraints related to the dynamical interactions in which they may have formed.

In this paper, I review some of the basic properties of the pulsar population in globular clusters (GCs) and compare it with the the Galactic disk population. The neutron stars (NSs) in GCs were likely formed - and appear to continue forming - in highly symmetric supernovae (SNe), likely from accretion-induced collapse (AIC). I review the many pulsar finds and discuss some particularly well populated GCs and why they are so. I then discuss some particularly interesting objects, like millisecond pulsars (MSPs) with eccentric orbits, which were heavily perturbed by passing stars. Some of these systems, like NGC 1851A and NGC 6544B, are almost certainly the result of exchange interactions, i.e., they are witnesses to the very same processes that created the large population of MSPs in the first place. I also review briefly the problem posed by the presence of young pulsars in GCs (with a special emphasis on a sub-class of young pulsars, the super-energetic MSPs), which suggest continuing formation of NSs in low-velocity SNe. In the final section, I discuss the possibility of an analogous population in the Galaxy and highlight a particularly interesting case, PSR J1903+0327, where the primary neutron star appears to have formed with a small-velocity kick and small fractional mass loss. Systems with primary NSs formed in electron-capture SNe should constitute a distinct low-velocity Galactic population akin in many respects to the GC population. Current high-resolution surveys of the Galactic plane should be able to detect it clearly.

The results of numerous spectroscopic and photometric studies have revealed the presence of multiple stellar populations in many globular clusters. In this paper we summarize the results of our recent studies on the dynamical evolution of multiple-population clusters, the implications of the structural properties of multiple-population clusters for the evolution of binary stars, and the possible contribution of globular clusters to the assembly of the Galactic halo.

We review spectroscopic evidence of multiple stellar populations in globular clusters. First, we lay down the basic data: the C-N, Na-O, Mg-Al anti-correlations among red giants and main sequence stars, and discuss how they appear to be general properties of globular clusters, in spite of cluster-to-cluster differences. We will then describe what is currently known about He from spectroscopy. We will then present the implications and current observations for the interpretation of the horizontal branches, showing that the multiple population phenomenon is strongly related to the distribution of stars along them. We will briefly mention the spectroscopic evidence related to some less understood cases, like the clusters with multiple subgiant branches. Finally, we summarize the relation between multiple populations and general properties for globular clusters, and their implications for the formation scenario.

The advent of the Hubble Space Telescope (HST) and the development of new photometric algorithms that take advantage of its stable observing platform above the atmosphere have allowed us to study the populations in globular clusters with very high precision.

Astronomical time series are special in that time sampling in them is uneven yet often with periodic gaps due to daytime, moon and seasons. There is therefore a need for special-purpose time-series analysis (TSA) methods. The emergence of massive CCD photometric surveys from the ground and space raises the question of an automatic period search in ≫ 105 light curves. We caution that already at the planning stage it is important to account for the effects of time sampling and analysis methods on the sensitivity of detections. We present a transparent scheme for the classification of period-search methods. We employ tools for evaluating the performance of those methods, according to the type of light curves investigated. In particular we consider sinusoidal and non-sinusoidal oscillations as well as eclipse or transit light curves. From these considerations we draw recommendations for the optimum analysis of astronomical time series. We present briefly the capability of an automatic period-search package Tatry. Finally we discuss the role of Monte Carlo simulations in the analysis of detection sensitivity. As an example, we demonstrate a practical method to account for the bandwidth (multi-trial) penalty in the statistical evaluation of detected periods.

We systematically study the effects of collisions on the overall dynamical evolution of dense star clusters using Monte Carlo simulations over many relaxation times. We derive many observable properties of these clusters, including their core radii and the radial distribution of collision products. We also study different aspects of collisions in a cluster taking into account the shorter lifetimes of more massive stars, which has not been studied in detail before. Depending on the lifetimes of the significantly more massive collision products, observable properties of the cluster can be modified qualitatively; for example, even without binaries, core collapse can sometimes be avoided simply because of stellar collisions.

We use numerical simulations to study how the spatial distribution and kinematics of globular cluster systems (GCS) are affected by galaxy mergers. Each progenitor galaxy is given a GCS modeled after the Galactic GCS. We then study how a major merger affects the spatial distribution and kinematics of the GCS. Here we present our methodology. Future work will investigate the effects of varying galaxy parameters, merger orbital parameters, and initial GCS number density profile and kinematics. We hope to be able to extract information about the merger history of a galaxy from observations of its GCS spatial distribution and kinematics.

We intend to map the differential extinction and remove their effects in a sample of clusters in the direction of the inner Galaxy using a new dereddening technique. These observations and their analyses will let us produce high quality color-magnitude diagrams of these poorly studied clusters that will allow us to determine these clusters' relative ages, distances and chemistry and to address important questions about the formation and the evolution of the inner Galaxy.

Globular clusters have been long predicted to host intermediate-mass black holes (IMBHs) in their centres. The growing evidence that some/all Galactic globular clusters (GCs) could harbour middle range (102 – 104M⊙) black holes, just as galaxies do, stimulates the searches and the development of new methods for proving their existence. Here we propose another method of detection – the microlensing of the cluster stars by the central BH.