相关论文: The Age of Cluster Galaxies from Continuum Colors
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…
Using up-to-date stellar models and isochrones we determine the age of 25 galactic halo clusters. The clusters are distributed into four groups according to metallicity. We measure the absolute age of a reference cluster in each group, and…
Most stars do not form in isolation but as part of a cluster comprising anywhere between a few dozen to several million stars with stellar densities ranging from 0.01 to several 10$^5$ \Msun pc$^{-3}$. The majority of these clusters…
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…
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 present age and metallicities determinations based on narrow band continuum colors for the galaxies in the rich clusters A1185 and Coma. Using a new technique to extract luminosity-weighted age and [Fe/H] values for non-star-forming…
An overview of our current understanding of the formation and evolution of star clusters is given, with main emphasis on high-mass clusters. Clusters form deeply embedded within dense clouds of molecular gas. Left-over gas is cleared within…
We establish a framework for determing absolute ages of Galactic globular clusters and then use these ages to investigate the age-metallicity and age-Galactocentric distance relations for the 36 clusters with the most reliable age data. The…
The degree of influence that environment and mass have on the stellar populations of early-type galaxies is uncertain. In this paper we present the results of a spectroscopic analysis of the stellar populations of early-type galaxies aimed…
To understand the evolution of galaxies, we need to know as accurately as possible how many galaxies were present in the Universe at different epochs. Galaxies in the young Universe have hitherto mainly been identified using their expected…
Star clusters are ideal tracers of star formation activity in systems outside the volume that can be studied using individual, resolved stars. These unresolved clusters span orders of magnitude in brightness and mass, and their formation is…
The population and population composition of galaxies in galaxy clusters at present reflect the mass of the clusters and the mass growth of the galaxies in the past. We investigate them for six clusters. We show that galaxies in massive…
Globular cluster ages are more than just lower limits to the age of the universe; the distribution of ages constraints the timescales for galaxy formation and chemical evolution. Globular cluster populations with different metallicities…
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…
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,…
Low-mass galaxies in nearby clusters are the most numerous galaxy type in the universe, yet their origin and properties remain largely unknown. To study basic questions concerning these galaxies we present the results of a survey designed…
We determine ages of 71 old Open Clusters by a two-step method: we use main-squence fitting to 10 selected clusters, in order to obtain their distances, and derive their ages from comparison with our own isochrones used before for 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…
Globular Cluster (GC) formation seems to be a widespread mode of star formation in extreme starbursts triggered by strong interactions and mergers of massive gas-rich galaxies. We use our detailed chemically consistent evolutionary…
We present an analysis of the positions and ages of young star clusters in eight local galaxies to investigate the connection between the age difference and separation of cluster pairs. We find that star clusters do not form uniformly but…