相关论文: Age Gradient and the Second Parameter Problem in t…
Our picture of the age-metallicity relation for Milky Way globular clusters (MWGCs) is still highly incomplete, and the majority of MWGCs lack self-consistent age measurements. Here, we exploit deep, homogenous multi-epoch Hubble Space…
Globular Cluster Systems (GCSs) of most early-type galaxies feature two peaks in their optical colour distributions. Blue-peak GCs are believed to be old and metal-poor, whereas the ages, metallicities, and the origin of the red-peak GCs…
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…
Various methods for age dating globular clusters in ellipticals are presented. We first present spectroscopy of individual globular clusters (feasible with the advent of the 10m-class telescopes), and the measurement of Balmer line indices.…
We here present our first attempt to use Globular Clusters as tracers of their parent galaxy's formation history. Globular Cluster Systems of most early-type galaxies feature two peaks in their optical colour distributions. Blue-peak…
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…
We present an analysis of the radial age gradients for the stellar halos of five Milky Way mass-sized systems simulated as part of the Aquarius Project. The halos show a diversity of age trends, reflecting their different assembly…
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…
Recent discoveries have put the picture of stellar clusters being simple stellar populations into question. In particular, the color-magnitude diagrams of intermediate age (1-2 Gyr) massive clusters in the Large Magellanic Cloud (LMC) show…
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…
It has been a long-standing open question why observed globular cluster (GC) populations of different metallicities differ in their ages and spatial distributions, with metal-poor GCs being the older and radially more extended of the two.…
We present an unbiased method for evaluating the ranges of ages and metallicities which are allowed by the photometric properties of the stellar populations that dominate the light of early-type galaxies in clusters. The method is based on…
Stromgren uvby CCD photometry can be used in a variety of ways to constrain the absolute and relative ages of globular clusters. The reddening corrected (v-y, c1) diagram offers the means to derive ages that are completely independent of…
The ages of globular clusters inferred from observations depends sensitively on assumptions like the initial helium abundance and the mass loss rate. A high helium abundance (e.g., $Y\approx$0.28) or a mass loss rate of…
We are using full spectrum fitting to determine the ages and metallicities of Galactic clusters (M67 and globular clusters). We find that the method is very accurate to measure the metallicity. Blue horizontal branches are well identified…
In some scenarios for the formation of the Milky Way bulge the stellar population at the edges of the boxy bulge may be younger than those on the minor axis, or close to the Galactic center. So far the only bulge region where deep…
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…
Aim of this study is to infer the age of the Galactic Disk by means of the ages of old open clusters, and comment on some recent claims that the Galactic Disk can be older than the Halo. To this purpose, we analyze the Color-Magnitude…
A comparison is made between the age-metallicity relation obtained from four different types of studies: F and G stars in the Solar Neighbourhood, analysis of open clusters, galactic structure studies with the stellar population synthesis…
Globular cluster systems exhibit a bewildering variety of characteristics. No single scenario appears to be able to account for the wide range of specific globular cluster frequencies that are observed in galaxies of various types. The…