Related papers: Horizontal-Branch Stars as an Age Indicator
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…
We present a study of the variation of spatial structure of stellar populations within dwarf galaxies as a function of the population age. We use deep Hubble Space Telescope/Advanced Camera for Surveys imaging of nearby dwarf galaxies in…
The fundamental plane (FP) has an intrinsic scatter that can not be explained purely by observational errors. Using recently available age estimates for nearby early type galaxies, we show that a galaxy's position relative to the FP depends…
Broadband colours are often used as metallicity proxies in the study of extragalactic globular clusters. A common concern is the effect of variations in horizontal branch (HB) morphology--the second-parameter effect--on such colours. We…
Cosmic chronometers may be used to measure the age difference between passively evolving galaxy populations to calculate the Hubble parameter H(z). The age estimator emerges from the relationship between the amplitude of the rest frame…
We present the UV photometry of the globular cluster NGC 1851 using images acquired with the Ultra-violet Imaging Telescope (UVIT) onboard the ASTROSAT satellite. PSF-fitting photometric data derived from images in two far-UV (FUV) filters…
If the stellar halos of disk galaxies are built up from the disruption of dwarf galaxies, models predict highly structured variations in the stellar populations within these halos. We test this prediction by studying the ratio of blue…
Age is one of the most fundamental parameters of stars, yet it is one of the hardest to determine as it requires modelling various aspects of stellar formation and evolution. When we compare the ages derived from isochronal and dynamical…
We investigate techniques that can be used to determine ages of recently star forming regions during the phase dominated in the near-IR by the asymptotic giant branch stars (10^8-10^9 yrs). In particular, we present selected near-IR…
Accurately determining the age of H\,{ii} regions and the stars they host is as important as it is challenging. Historically the most popular method has been isochrone fitting to Hertzsprung-Russell Diagrams or Colour-Magnitude Diagrams.…
Determination of stellar age is a crucial task in astrophysics research. Different methods are nowadays used either model dependent or based on calibrated empirical relations. The most reliable results are generally obtained when different…
omega Cen contains the largest population of very hot horizontal branch (HB) stars known in a globular cluster. Recent UV observations (Whitney et al. 1998; D'Cruz et al. 2000) show a significant population of hot stars below the zero-age…
Discovery of the first planetary system by direct imaging around HR8799 has made the age determination of the host star a very important task. This determination is the key to derive accurate masses of the planets and to study the dynamical…
We report here initial but still strongly conclusive results on absolute ages of galactic globular clusters (GGCs). This study is based on high precision trigonometric parallaxes from the HIPPARCOS satellite coupled with accurate metal…
We test the hypothesis that the apparent axis ratio of an elliptical galaxy is correlated with the age of its stellar population. We find that old ellipticals (with estimated stellar ages t > 7.5 Gyr) are rounder on average than younger…
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 next generation near- and mid-infrared Galactic surveys will yield a large number of new highly obscured star clusters. Detailed characterization of these new objects with spectroscopy is time-consuming. Diagnostic tools that will be…
We study the propagation of star formation based on the investigation of the separation of young star clusters from HII regions nearest to them. The relation between the separation and U-B colour index (or age) of a star cluster was found.…
The physical parameters of the stars in the central region of the globular cluster M5 (NGC 5904) were determined from UBV photometry using Kurucz (1992) synthetic flux distributions and some empirical relations. It is found that the bluest…
The HST data archive contains images of several nearby spirals, suitable for detailed studies of the properties of individual star clusters and their surroundings. By combining structural information derived from HST images with…