Related papers: Horizontal branch morphology in galactic globular …
The high spatial resolution of the Hubble Space Telescope (HST) has led to tremendous progress in many areas of astronomy. The ability of the HST to peer into the bright inner regions of galaxies and distinguish between globular clusters…
We have explored the role environmental factors play in determining characteristics of young stellar objects in nearby dwarf irregular and Blue Compact Dwarf galaxies. Star clusters are characterized by concentrations, masses, and formation…
Recent progress in studies of globular clusters has shown that they are not simple stellar populations, being rather made of multiple generations. Evidence stems both from photometry and spectroscopy. A new paradigm is then arising for the…
Blue horizontal-branch (BHB) stars with $T_{\rm eff}$ approximately larger than 11500 K show several observational anomalies. In globular clusters, they exhibit low rotational velocities, abundance anomalies (as compared to cluster…
In order to investigate the nature of dwarf Low Surface Brightness (LSB) galaxies we have undertaken a deep B and I band CCD survey of a 14 sq degree strip in the Virgo Cluster and applied a Fourier convolution technique to explore its…
As part of a large project aimed at characterizing the ultraviolet (UV) properties of globular clusters, we present here a theoretical and observational analysis aimed at setting the framework for the determination of horizontal branch (HB)…
The distribution of Milky Way halo blue horizontal-branch (BHB) stars is examined using action-based extended distribution functions (EDFs) that describe the locations of stars in phase space, metallicity, and age. The parameters of the…
Cosmological simulations predict significant secondary dependencies of halo clustering on internal properties and environment. Detecting these subtle signals in observational data remains challenging, with important ramifications for galaxy…
A significant fraction of stars in globular clusters (about 70%-85%) exhibit peculiar chemical patterns with strong abundance variations in light elements along with constant abundances in heavy elements. These abundance anomalies can be…
We have determined the projected rotational velocities of thirteen blue horizontal-branch (BHB) stars in the globular cluster M13 via rotational broadening of metal absorption lines. Our sample spans the photometric gap observed in the…
Deep UBVI photometry for a large field covering the distant globular cluster M75 (NGC 6864) is presented. We confirm a previous suggestion (Catelan et al. 1998a) that M75 possesses a bimodal horizontal branch (HB) bearing striking…
Blue horizontal-branch (BHB) stars are old, low-mass, metal-poor stars that serve as important tracers of the Galactic halo structure, kinematics, and evolution.Understanding their binary properties provides key insights into their…
We report the discovery of a peculiar horizontal branch (HB) in NGC 6440 and NGC 6569, two massive and metal-rich Galactic globular clusters (GGCs) located in the Galactic bulge, within 4 kpc from the Galactic Center. In both clusters, two…
The morphology of the Horizontal Branch (HB) in Globular Clusters (GC) is among the early evidences that they contain multiple populations of stars. Indeed, the location of each star along the HB depends both on its initial helium content…
We discuss the state of the assembly of the Hubble Sequence in the mix of bright galaxies at redshift 1.4< z \le 2.5 with a large sample of 1,671 galaxies down to H_{AB}~26, selected from the HST/ACS and WFC3 images of the GOODS--South…
Integrated spectroscopy is the method of choice for deriving the ages of unresolved stellar systems. However, hot stellar evolutionary stages, such as hot horizontal branch stars and blue straggler stars (BSSs), can affect the integrated…
The morphology of clusters of galaxies may be described with a set of parameters which contain information about the formation and evolutionary history of these systems. In this paper we present a preliminary study of the morphological…
It has recently been suggested that the presence of multiple populations showing various amounts of helium enhancement is the rule, rather than the exception, among globular star clusters. An important prediction of this helium enhancement…
Multiple stellar populations (MPs) are a distinct characteristic of Globular Clusters (GCs). Their general properties have been widely studied among main sequence, red giant branch (RGB) and horizontal branch (HB) stars, but a common…
We have developed an homogeneous evolutionary scenario for H- and He-burning low-mass stars by computing updated stellar models for a wide metallicity and age range (0.0002$\le Z \le$0.004 and 9$\le t(Gyr) \le$15, respectively) suitable to…