Related papers: Horizontal Branch Morphology and the 2nd Parameter…
Photometric surveys with the Hubble Space Telescope (HST) allow us to study stellar populations with high resolution and deep coverage, with estimates of the physical parameters of the constituent stars being typically obtained by comparing…
In this paper we investigate the relation between the detailed isophotal shape of elliptical galaxies and the strength of the H beta absorption in their spectra. We find that disky galaxies have higher H beta indices. Stellar population…
The diagnostic age versus mass-to-light ratio diagram is often used in attempts to constrain the shape of the stellar initial mass function, and the stability and the potential longevity of extragalactic young to intermediate-age massive…
We report on HST/WFPC2 U,V and far-ultraviolet observations of two Galactic Globular Clusters (GGCs), NGC 6205 = M13 and NGC 6093 = M80. Both of these clusters have horizontal-branch (HB) tails that extend to the helium-burning main…
Recent work, based on data from the Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GCs), has revealed that all the analyzed clusters host two groups of first- (1G) and second-generation (2G) stars. In most GCs,…
We have developed an homogeneous evolutionary scenario for H- and He-burning low-mass stars by computing updated stellar models for a wide metallicity and age range (0.0002$\le Z \le$0.004 and 9$\le t(Gyr) \le$15, respectively) suitable to…
We analyze the angular momentum evolution from the red giant branch (RGB) to the horizontal branch (HB) and along the HB. Using rotation velocities for stars in the globular cluster M13, we find that the required angular momentum for the…
Recent HST observations of the metal-rich bulge clusters NGC 6388 and NGC 6441 by Rich et al. (1997) have found that the horizontal branches (HBs) in these clusters slope upward with decreasing B-V. Such an upward slope in the HB morphology…
Grids of zero-age horizontal branch (ZAHB) models are presented, along with a suitable interpolation code, for -2.5 <= [Fe/H] <= -0.5, in steps of 0.2 dex, assuming Y = 0.25 and 0.29, [O/Fe] = +0.4 and +0.6, and [m/Fe] = 0.4 for all of the…
An analysis of available Galactic globular cluster data on metallicity, ages, the distribution of stars on the horizontal branch and the distribution of the periods of RR0 Lyr variables showed that: 1. The latter two characteristics can be…
We use the framework developed as part of the MESA Isochrones and Stellar Tracks (MIST) project to assess the utility of several types of observables in jointly measuring the age and 1D stellar model parameters in star clusters. We begin…
The globular cluster M79 was observed with the Hopkins Ultraviolet Telescope (HUT) during the Astro-1 space shuttle mission in 1990 December. The cluster's far-UV integrated spectrum shows strong absorption in the Lyman lines of atomic…
We have completely mapped the globular cluster NGC 1851 with VI CCD photometry, obtaining a CMD for ca. 20500 stars. From the apparent luminosity of the HB we derive a distance modulus (m-M)o=15.44+/-0.20. The presence of 7 "supra-HB" stars…
The UV properties of old stellar populations have been subject of intense scrutiny from the late sixties, when the UV-upturn in early type galaxies was first discovered. Because of their proximity and relative simplicity, Galactic globular…
In a previous paper we reported on a discontinuity in the extreme horizontal branch (EHB) of the Galactic globular cluster NGC6752, which we called the second U-jump. This feature was attributed to a combination of post zero-age horizontal…
M31 hosts a rich population of outer halo ($R_{\rm{proj}} > 25$ kpc) globular clusters (GCs), many of which show strong evidence for spatial and/or kinematical associations with large-scale tidal debris features. We present deep Hubble…
Globular clusters (GCs) are known to host multiple stellar populations showing chemical anomalies in the content of light elements. The origin of such anomalies observed in Galactic GCs is still debated. Here we analyse data compiled from…
Several observations of the central region of the Hydra I galaxy cluster point to a multi-epoch assembly history. Using our novel FORS2/VLT spectroscopic data set, we were able to map the luminosity-weighted age, [Fe/H] and [$\alpha$/Fe]…
The horizontal branch (HB) phase of stellar evolution plays a critical role in understanding the life cycle of stars, particularly in the context of low-mass stars. However, generating theoretical evolutionary tracks for HB stars is…
We have assembled a catalogue of relative ages, metallicities and abundance ratios for about 150 local galaxies in field, group and cluster environments. The galaxies span morphological types from cD and ellipticals, to late type spirals.…