Related papers: Three Parameters for the Horizontal-Branch Morphol…
Mergers of globular clusters (GCs) once associated with dwarf spheroidal (dSph) galaxies have recently been suggested as an explanation for the bimodal horizontal branches (HBs) of some Galactic GCs, most notably NGC 1851, NGC 2808, and NGC…
Context. Abundance anomalies have been observed in field sdB stars and in nearly all Horizontal Branch (HB) stars of globular clusters with Teff > 11 000K whatever be the cluster metallicity. Aims. The aim is to determine the abundance…
We report on HST/WFPC2 U,V and far-ultraviolet observations of two Galactic Globular Clusters (GGCs), NGC 6205 = M13 and NGC 6093 = M80. Both of these clusters have horizontal-branch (HB) tails that extend to the helium-burning main…
Recent work, based on data from the Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GCs), has revealed that all the analyzed clusters host two groups of first- (1G) and second-generation (2G) stars. In most GCs,…
We have used WFPC2 to construct B, V color-magnitude diagrams of four metal-rich globular clusters, NGC 104 (47 Tuc), NGC 5927, NGC 6388, and NGC 6441. All four clusters have well populated red horizontal branches (RHB), as expected for…
We use the Stetson, HST, and Gaia DR3 data sets for 22 Galactic globular clusters to select their members and fit their CMDs with isochrones from DSED and BaSTI for $[\alpha/$Fe$]=+0.4$ and an adopted helium mass fraction $Y$. As a result,…
About 25% of the Milky Way globular clusters (GCs) exhibit unusually extended color distribution of stars in the horizontal-branch (HB) phase. This phenomenon is now best understood as due to the presence of helium enhanced second…
We present high-precision V, B-V color-magnitude diagrams (CMDs) for the classic second parameter globular clusters M3 and M13 from wide-field deep CCD photometry. The data for the two clusters were obtained during the same photometric…
We exploit multi-band Hubble Space Telescope photometry to investigate multiple populations (MPs) along the red horizontal branches (HBs) and red clumps of fourteen metal-rich Globular Clusters (GCs), including twelve Milky Way GCs and the…
JHK images obtained with the Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Bonnette (AOB) are used to investigate the near-infrared photometric properties of red giant branch (RGB) and horizontal branch (HB) stars in eight…
Red giants are an excellent tool for probing the history of star formation and subsequent metallicity evolution in the galaxies. The well-defined red giant branch (RGB) stars of the globular clusters can be used to determine their slopes…
We present the results of a first global analysis of the Horizontal Branch morphology of Globular Clusters in the nearby spiral M31, based on their Color Magnitude Diagrams.
Globular cluster (GC) systems around galaxies of a vast mass range show remarkably simple scaling relations. The combined mass of all GCs is a constant fraction of the total galaxy mass and the mean metallicity and metallicity dispersion of…
The determination of stellar metallicity and its gradient in external galaxies is a difficult task, but crucial for the understanding of galaxy formation and evolution. The color of the Red Giant Branch (RGB) can be used to determine…
I review aspects of the evolution of horizontal branch (HB) stars. I start by discussing current topics in the study of HB stellar evolution, including a brief review of the main determinants of the structure of low-mass core helium burning…
We perform an evolutionary multivariate analysis of a sample of 54 Galactic globular clusters with high-quality colour-magnitude diagrams and well-determined ages. The four parameters adopted for the analysis are: metallicity, age, maximum…
We investigate the structural, kinematical, and chemical properties of globular cluster systems (GCSs) in galaxies of different Hubble types in a self-consistent manner based on high-resolution cosmological N-body simulations combined with…
We report new, as yet unpublished HST/WFPC2 V, I photometry of 9 globular clusters in M31. These are part of a total sample of 19 clusters on M31 with well observed CMDs from HST. The clusters have the full range of horizontal branch…
Aims. We use the spectra of more than 30,000 red giant branch (RGB) stars in 25 globular clusters (GC), obtained within the MUSE survey of Galactic globular clusters, to calibrate the Ca II triplet (CaT) metallicity relation and derive…
Hubble Space Telescope imaging for 26 giant early-type galaxies, all drawn from the MAST archive, is used to carry out photometry of their surrounding globular cluster (GC) systems. Most of these targets are Brightest Cluster Galaxies…