相关论文: Theoretical vs. semi-empirical relative ages of gl…
I review here recent developments which have affected our understanding of both the absolute age of globular clusters and the uncertainties in this age estimate, and comment on the implications for cosmological models. This present estimate…
We report the results of a detailed numerical study designed to estimate both the absolute age and the uncertainty in age (with confidence limits) of the oldest globular clusters. Such an estimate is essential if a comparison with the…
We present accurate relative ages for a sample of 55 Galactic globular clusters. The ages have been obtained by measuring the difference between the horizontal branch and the turnoff in two, internally photometrically homogeneous databases.…
We discuss the present state of knowledge and thought concerning the spread in age found among Galactic globular clusters, with some discussion of the implications for what happened during the earliest stages of the formation of the Milky…
The main sequence turnoff luminosity is the best stellar `clock' which can be used to determine the absolute ages of globular clusters. This is due to the fact that it is generally assumed that the luminosity and lifetimes of main sequence…
Ages of extragalactic globular clusters can provide valuable insights into the formation and evolution of galaxies. In this contribution the photometric methods of age dating old globular cluster systems are summarised. The spectroscopic…
We present a review of the present state of knowledge regarding the relative ages of Galactic globular clusters. First, we discuss the relevant galaxy formation models and describe the detailed predictions they make with respect to the…
We review five independent techniques which are used to set the distance scale to globular clusters, including subdwarf main sequence fitting utilizing the recent Hipparcos parallax catalogue. These data together all indicate that globular…
We present an estimate of the absolute age of 68 galactic globular clusters obtained by exploiting the distribution of stars in the full color-magnitude diagram. In particular, we jointly estimate the absolute age, distance, reddening,…
Globular clusters are the oldest objects in the Galaxy whose age may be accurately determined. As such globular cluster ages provide the best estimate for the age of the universe. The age of a globular cluster is determined by a comparison…
In previous papers of the series we used a combination of optical and near-infrared colours to derive constraints on the relative age structure in globular cluster systems. Here, we present the details, strength and limitations of our…
We present preliminary results from our on-going survey of Galactic globular clusters relative ages. The investigation is based on V,I images obtained at the ESO and La Palma telescopes, which make up the largest homogenous photometric…
Age constraints are most often placed on globular clusters by comparing their CMDs with theoretical isochrones. The recent discoveries of detached, eclipsing binaries in such systems by the Cluster AgeS Experiment (CASE) provide new…
We revisit the determination of the age of the Universe from galactic globular clusters, extending previous analyses by explicitly accounting for the presence of multiple stellar populations within each cluster. Using high--quality…
A new grid of theoretical isochrones based on the Yale stellar evolution code using the OPAL and Kurucz opacities has been constructed. The grid of isochrones spans a wide range of metallicities, helium abundances and masses. The…
Based on a new large, homogeneous photometric database of 35 Galactic globular clusters (GGCs), a set of distance and reddening independent relative age indicators has been measured. The observed D(V-I)_2.5 and D(V)(HB-TO) vs. metallicity…
We present a statistical approach for determining the age of Globular Clusters (GCs) that allows estimating the age derived from CMDs more accurately than the conventional methods of the isochrone fitting. We measure how closely a set of…
We present a statistical approach for estimating the age of Globular Clusters by measurement of the likelihood between the observed cluster sequences in the Colour--Magnitude Diagram and the synthetic cluster sequences computed from stellar…
The ACS Survey of Galactic Globular Clusters is a Hubble Space Telescope (HST) Treasury program designed to provide a new large, deep and homogeneous photometric database. Based on observations from this program, we have measured precise…
The ages of star clusters and co-moving stellar groups contain essential information about the Milky Way. Their special properties make them excellent tracers of galactic structure and key components to unlocking its star formation history.…