Related papers: Horizontal-Branch Stars as an Age Indicator
We present our recent revision of model constructions for the horizontal-branch (HB) morphology of globular clusters, which suggests the HB morphology is more sensitive to age compared to our earlier models. We also present our high…
The strength of the H$\beta$ index has been computed for the integrated spectra of model globular clusters from the evolutionary population synthesis. These models take into account, for the first time, the detailed systematic variation of…
After taking into account, for the first time, the detailed systematic variation of horizontal-branch (HB) morphology with age and metallicity, our population synthesis models show that the integrated H beta index is significantly affected…
Theory and observations indicate that the distribution of stars along the horizontal branch of Galactic globular clusters mainly depends on the metal content. However, the existence of globular clusters with similar metal content and…
Theoretical integrated broad-band colors ranging from far-UV to near-IR have been computed for old stellar systems from our evolutionary population synthesis code. These models take into account, for the first time, the detailed systematic…
We review the most outstanding issues related to the study of the morphology of the Horizontal Branch (HB) in the Color-Magnitude Diagrams of Galactic Globular Clusters and its use as age indicator. It is definitely demonstrated (see also…
We have applied a new method to analyze the horizontal branch (HB) morphology in relation to the distribution of stars near the red giant branch (RGB) tip for the globular clusters M22, M5, M68, M107, M72, M92, M3 and 47 Tuc. This new…
A major source of uncertainty in the age determination of old ($\sim10$ Gyr) integrated stellar populations is the presence of hot horizontal branch (HB) stars. Here, we describe a simple approach to tackle this problem, and show the…
The effects of blue horizontal-branch (HB) stars on the integrated spectrophotometric indices of simple stellar populations (SSPs) are addressed. Synthetic spectra are drawn from a grid of simulated globular clusters, constructed so as to…
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)…
A major uncertainty in the spectroscopic dating of extragalactic globular clusters concerns the degenerate effect that age and horizontal branch morphology have on the strength of Balmer lines. In this Letter we show that the ratio between…
We present a new method for measuring the mean age of old/intermediate stellar populations in resolved, metal-poor ($\rm \langle[Fe/H]\rangle \lesssim -1.5$) galaxies using only the morphology of the horizontal branch (HB) and an estimate…
Horizontal branch (HB) stars play a particularly important role in the "age debate," since they are at the very center of the long-standing "second parameter" problem. In this review, I discuss some recent progress in our understanding of…
Globular clusters offer ideal laboratories to test the predictions of stellar evolution. When doing so with spectroscopic analyses during the 1990s, however, the parameters we derived for hot horizontal branch stars deviated systematically…
The presence of an extended blue horizontal branch (HB) in a stellar population is known to affect the age inferred from spectral fitting to stellar population synthesis models. However, most population synthesis models still rely on…
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 Horizontal Branch (HB) morphology in the color -- magnitude diagram of the Galactic globular clusters depends on many factors, and it is now firmly established that the so-called Second Parameter is not just the cluster age as claimed…
Isochrone computations and horizontal branch (HB) models for Y(MS)=0.23 and two values of Z (0.0001, 0.0004)are used to derive constraints on the age indicators and HB morphology of metal-poor clusters with age t (in Gyrs) in the range of…
The interpretation of globular cluster horizontal branch (HB) morphology is a classical problem that can significantly blur our understanding of stellar populations. In this paper, we present a new multivariate analysis connecting the…
Ages have been derived for 55 globular clusters (GCs) from overlays of isochrones onto the turnoff photometry, assuming distances based on fits of zero-age horizontal branch (ZAHB) models to the lower bound of the observed distributions of…