Related papers: Galactic Globular Cluster Relative Ages. II
We present new high signal-to-noise spectroscopic data on the M31 globular cluster system, obtained with the Hectospec multifiber spectrograph on the 6.5m MMT. More than 300 clusters have been observed at a resolution of 5A. The primary…
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…
JWST observations of the strongly lensed galaxy The Sparkler have revealed a population of gravitationally bound globular cluster (GC) candidates. Different analyses have resulted in broadly similar ages but significantly different…
We derive ages, metallicities and [alpha/Fe] ratios from the integrated spectra of 23 globular clusters in M31, by employing multivariate fits to two stellar population models. In parallel we analyze spectra of 21 Galactic globular clusters…
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…
Globular cluster (GC) systems around galaxies of a vast mass range show remarkably simple scaling relations. The combined mass of all GCs is a constant fraction of the total galaxy mass and the mean metallicity and metallicity dispersion of…
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…
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…
The color distributions of globular clusters (GCs) in individual early-type galaxies show great diversity in their morphology. Based on the conventional "linear" relationship between the colors and metallicities of GCs, the GC metallicity…
A subset of 150 globular clusters in M87 has been selected on the basis of S/N ratio for abundance and age determinations from the sample of Paper I. Indices measuring the strength of the strongest spectral features were determined for the…
We here present the results of an analysis of the optical spectroscopy of 42 globular cluster (GC) candidates in the nearby spiral galaxy M81 (3.61~Mpc). The spectra were obtained using the long-slit and MOS modes of the OSIRIS instrument…
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…
We have investigated the formation of globular cluster (GC) systems in the fiducial semi-analytic galaxy formation model of Cole et al. We assume that GCs are formed at high-redshift (z > 5) in proto-galactic fragments, and during the…
We present the results of a meta-analysis of Keck spectra of extragalactic globular clusters (GCs) in a sample of eight galaxies, ranging from dwarfs to massive ellipticals. We infer ages for the metal-poor and metal-rich GCs in these…
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…
In this paper, we are exploring the properties of old, metal-poor globular clusters in galaxies. We investigate whether their properties are related to the properties of their host galaxies, and whether we can constrain their formation. 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…
We present measurements of ages, metallicities, and [alpha/Fe] ratios for 16 globular clusters (GC) in NGC 147, NGC 185, and NGC 205 and of the central regions of the diffuse galaxy light in NGC 185, and NGC 205. Our results are based on…
The dominant systematic uncertainty in the age determination of galactic globular clusters is the depth of the convection envelope of the stars. This parameter is partially degenerate with metallicity which is in turn degenerate with age.…
We use recently derived ages for 61 Milky Way (MW) globular clusters (GCs) to show that their age-metallicity relation (AMR) can be divided into two distinct, parallel sequences at [Fe/H] $\ga -1.8$. Approximately one-third of the clusters…