Related papers: Multiple Population Theory: Extreme helium populat…
Evidence that the multiple populations (MPs) are common properties of globular clusters (GCs) is accumulated over the past decades from clusters in the Milky Way and in its satellites. This finding has revived GC research, and suggested…
Observations revealed the presence of multiple stellar populations in globular clusters (GCs) that exhibit wide abundance variations and multiple sequences in Hertzsprung-Russell (HR) diagram. We present a scenario for the formation of…
In this contribution I am going to present some preliminary results of a high-resolution spectroscopic campaign focussed on the most metal rich red giant stars in Omega Cen. This study is part of a long term project we started a few years…
Galactic Globular clusters (GCs) are now known to harbour multiple stellar populations, which are chemically distinct in many light element abundances. It is becoming increasingly clear that asymptotic giant branch (AGB) stars in GCs show…
Various galactic globular clusters display abundance anomalies that affect the morphology of their colour-magnitude diagrams. In this paper we consider the possibility of helium enhancement in the anomalous horizontal branch of NGC 2808. We…
One of the challenges for stellar astrophysics is to reach the point at which we can undertake reliable spectral synthesis of unresolved populations in young, star-forming galaxies at high redshift. Here I summarise recent studies of…
The detection of star-to-star chemical variations in star clusters older than 2 Gyr has changed the traditional view of star clusters as canonical examples of "simple stellar populations" (SSPs) into the so-called "multiple stellar…
Helium is the second most common chemical species in the Universe. The study of helium abundance has the potential to unravel the chemical evolution of and within galaxies. In this study, we provide an empirical calibration for the singly…
The "stellar" solution to the cosmological lithium problem proposes that surface depletion of lithium in low-mass, metal-poor stars can reconcile the lower abundances found for Galactic halo stars with the primordial prediction. Globular…
Context. Omega Cen is the largest known globular cluster in the Milky Way. It is also quite a complex object with a large metallicity spread and multiple stellar populations. Despite a number of studies over the past several decades, the…
We present an analysis of optical and ultraviolet Hubble Space Telescope photometry for evolved stars in the core of the distant massive globular cluster NGC 2419. We characterize the horizontal branch (HB) population in detail including…
We demonstrate that among the potential sources of the primordial abundance variations of the proton-capture elements in globular-cluster stars proposed so far, such as the hot-bottom burning in massive AGB stars and H burning in the…
The galactic globular cluster Omega Centauri is the most massive of its kind, with a complex mix of multiple stellar populations and several kinematic and dynamical peculiarities. Different mean proper motions have been detected among the…
Globular cluster stars show chemical abundance patterns typical of hot-CNO processing. Lithium is easily destroyed by proton capture in stellar environments, so its abundance may be crucial to discriminate among different models proposed to…
We present an accurate analysis of the peculiar Horizontal Branch (HB) of the massive Galactic globular cluster NGC 2808, based on high-resolution far-UV and optical images of the central region of the cluster obtained with HST. We confirm…
Optical and near-IR observations of the halos of disk galaxies and blue compact galaxies have revealed a very red spectral energy distribution, which cannot easily be reconciled with a normal, metal-poor stellar population like that in the…
Abundance anomalies observed in globular cluster stars indicate pollution with material processed by hydrogen burning. Two main sources have been suggested: asymptotic giant branch (AGB) stars and massive stars rotating near the break-up…
The nature and formation history of our Galaxy's largest and most enigmatic stellar cluster, known as Omega Centauri (ocen) remains debated. Here, we offer a novel approach to disentangling the complex stellar populations within ocen based…
In this brief overview of the stellar populations of galaxies in clusters I highlight some of the most recent results, including the downsizing of the k+a population and the star formation--local density relation. I conclude discussing some…
Accurate photometry with HST/ACS shows that the main sequence of the globular cluster NGC 2808 splits into three separate branches. The three MS branches may be associated with complexities of the cluster's horizontal branch and of its…