Related papers: Implications of the WMAP Age Measurement for Stell…
We combine N-body simulations of structure growth with physical modelling of galaxy evolution to investigate whether the shift in cosmological parameters between the 1-year and 3-year results from the Wilkinson Microwave Anisotropy Probe…
Deriving precise stellar ages is a challenging task. Consequently, age-dependent relations - such as the age-metallicity and age-velocity dispersion relations of the Milky Way, or the age-rotation-activity relation of low-mass stars - are…
The dynamical age of the universe depends upon the rate of the expansion of the universe, which explicitly involves the dark energy equation of state parameter $w(z)$. Consequently, the evolution of $w(z)$ has a direct imprint on the age of…
Hierarchical star formation leads to a progressive decrease in the clustering of star clusters both in terms of spatial scale and age. Consistently, the statistical analysis of positions and ages of clusters in the Milky Way disk strongly…
The ages of young star clusters are fundamental clocks to constrain the formation and evolution of pre-main-sequence stars and their protoplanetary disks and exoplanets. However, dating methods for very young clusters often disagree,…
Deep Hubble Space Telescope (HST) observations with WFPC2 of the nearby globular cluster NGC 6752 have allowed us to obtain accurate photometry for the cluster white dwarfs (WD). A sample of local WDs of known trigonometric parallax and…
We infer the ages of three young stellar clusters, NGC 2004, NGC 7419, and NGC 2100, using Stellar Ages, a statistical algorithm designed to infer stellar population properties from color magnitude diagrams. Recent studies have revealed…
We constrain several models of the early Universe that predict a statistical anisotropy of the cosmic microwave background (CMB) sky. We make use of WMAP9 maps deconvolved with beam asymmetries. As compared to previous releases of WMAP…
The discovery of the quasar, the APM 08279+5255 at z = 3.91 whose age is 2-3 Gyr has once again led to ``age crisis''. The noticeable fact about this object is that it cannot be accommodated in a universe with $\Omega_m = 0.27$, currently…
Observational constraints to a large class of decaying vacuum cosmologies are derived using the angular size data of compact radio sources and the latest age estimates of globular clusters. For this class of deflationary $\Lambda(t)$…
The WFPC2 camera on HST has been used to obtain deep main sequence photometry of the low-metallicity ([Fe/H]=-2.14), outer-halo globular cluster NGC 2419. A differential fit of the NGC 2419 CMD to that of the similarly metal-poor \ standard…
[Abridged] We map the stellar age distribution ($\lesssim 1$ Gyr) across a 6kpc$\,\times\,$6kpc area of the Galactic disc to constrain our Galaxy's recent star-formation history. Our modelling draws on the sample of Zari et al. (2021) that…
We consider particle decays during the cosmic dark ages with two aims: (1) to explain the high optical depth reported by WMAP, and (2) to provide new constraints to the parameter space for decaying particles. We delineate the decay channels…
We present our new, fully-automated method to detect and measure the ages of star clusters in nearby galaxies, where individual stars can be resolved. The method relies purely on statistical analysis of observations and Monte-Carlo…
Most young stars in nearby molecular clouds have estimated ages of 1-2 Myr, suggesting that star formation is rapid. However, small numbers of stars in these regions with inferred ages of >= 5-10 Myr have been cited to argue that star…
We discuss some of the key open questions regarding the formation and evolution of globular clusters (GCs) during galaxy formation and assembly within a cosmological framework. The current state-of-the-art for both observations and…
Using the technique of Angulo & White (2010) we scale the Millennium and Millennium-II simulations of structure growth in a LCDM universe from the cosmological parameters with which they were carried out (based on first-year results from…
We derive a complementary cosmological upper bound on the fraction of dark matter residing inside massive compact halo objects (MACHOs) using the cosmic dawn and dark ages global 21-cm signal $(T_{21})$. MACHOs of masses $M\gtrsim…
WMAP observations have accurately determined the position of the first two peaks and dips in the CMB temperature power spectrum. These encode information on the ratio of the distance to the last scattering surface to the sound horizon at…
We present a new method for the evaluation of the age and age-spread among pre-main-sequence (PMS) stars in star-forming regions in the Magellanic Clouds, accounting simultaneously for photometric errors, unresolved binarity, differential…