相关论文: The Age of the Universe with Globular Clusters: Re…
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,…
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…
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…
This is the third article in a series aimed at computing accurate and precise ages of galactic globular clusters from their full color-magnitude diagram in order to estimate the age of the Universe and in turn constrain the cosmological…
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 the past 40 years a considerable effort has been focused in determining the age of the Universe at zero redshift using several stellar clocks. In this review I will describe the best theoretical methods to determine the age of the oldest…
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…
We extend our previous method to determine globular cluster ages using the luminosity function (Jimenez \& Padoan 1996). We show that the luminosity function depends on both age and distance modulus and that it is possible to distinguish…
Globular clusters are the oldest conglomerates of stars in our Galaxy and can be useful laboratories to test theories from stellar evolution to cosmology. In this paper, we present a new method to estimate the absolute age of a globular…
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…
Estimating the age of the Universe is an old problem. Rapid progress in observational cosmology in recent years has led to more accurate values of the fundamental parameters. The current most popular model is a flat Universe, with about 30%…
One of the largest sources of uncertainty in the computation of globular cluster isochrones and hence in the age determination of globular clusters is the lack of a rigorous description of convection. Therefore, we calibrated the…
We present a new method to compute stellar ages in Globular Clusters (GC) that is ten times more precise than the traditional isochrone fitting procedure. The method relies on accurate stellar evolutionary tracks and on photometry for GCs…
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…
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 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.…
The age of globular clusters inferred from observations depends sensitively on assumptions such as the initial helium abundance and the mass loss rate. A high helium abundance (e.g., $Y\approx$0.28), as well as an inclusion of helium…
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…
Globular cluster age estimates based on the absolute magnitude of the main sequence turn-off (\mvto) are generally considered to be the most reliable from a theoretical viewpoint. However, the difficulty in determining \mvto\ in observed…
New estimates of globular cluster distances, combined with revised ranges for input parameters in stellar evolution codes and recent estimates of the earliest redshift of cluster formation allow us to derive a new 95% confidence level lower…