Related papers: Horizontal branch morphology in galactic globular …

We review the available empirical evidence for the presence of "gaps" and multimodal distributions among horizontal branch (HB) stars, along with some of the theoretical scenarios that have been proposed to explain these features. While…

The presence of an extended blue horizontal branch (HB) in a stellar population is known to affect the age inferred from spectral fitting to stellar population synthesis models. However, most population synthesis models still rely on…

Morphological aspects of the $V, \bv$ diagram of metal-rich globular clusters are analyzed, on the basis of stellar evolution models for horizontal-branch (HB) and red giant branch stars. These have been incorporated into detailed synthetic…

The location of Galactic Globular Clusters' (GC) stars on the horizontal branch (HB) should mainly depend on GC metallicity, the "first parameter", but it is actually the result of complex interactions between the red giant branch (RGB)…

We present BV photometry of the Sculptor dwarf galaxy to V=22. These data give evidence for a bimodality in Sculptor's metallicity distribution based on a discontinuity in the luminosities of horizontal branch (HB) stars and by the presence…

The "second-parameter effect" is characterized by the existence of globular clusters (GCs) with similar metallicity [Fe/H] (the "first parameter") but different horizontal-branch (HB) morphologies. One of the primary second-parameter…

Ages have been derived for 55 globular clusters (GCs) from overlays of isochrones onto the turnoff photometry, assuming distances based on fits of zero-age horizontal branch (ZAHB) models to the lower bound of the observed distributions of…

Color-magnitude diagrams from deep, wide-field CCD photometry of the Sculptor dwarf spheroidal galaxy reveal that the red horizonal branch (RHB) stars are strongly concentrated towards the center of the galaxy relative to the dominant old…

Globular clusters offer ideal laboratories to test the predictions of stellar evolution. When doing so with spectroscopic analyses during the 1990s, however, the parameters we derived for hot horizontal branch stars deviated systematically…

We have constructed color-magnitude diagrams (CMDs) for ten globular clusters in the halo of the nearby spiral galaxy M33 based on Hubble Space Telescope Wide-Field Planetary Camera 2 observations in the F555W (~V) and F814W (~I) filters.…

The formation of populous secondary star cluster systems is a widespread phenomenon in mergers of gas-rich galaxies. Many, if not most, of those clusters are massive and compact enough to be young globular clusters (GCs). GC systems in most…

We study the globular clusters M3 and Palomar 3 as a "second parameter (2ndP) pair," showing that: i) M3 has a surprisingly strong *internal* 2ndP; ii) The dispersion in mass on the Pal 3 horizontal branch (HB) is intrinsically very small,…

High-resolution optical spectra of thirteen blue horizontal-branch (BHB) stars in the globular cluster M13 show enormous deviations in element abundances from the expected cluster metallicity. In the hotter stars (T_eff > 12000 K), helium…

We present an analysis of high-quality photometry for globular clusters (GCs) in the Virgo cluster core region, based on data from the Next Generation Virgo Cluster Survey (NGVS) pilot field, and in the Milky Way (MW) based on VLT/X-Shooter…

This paper is a further step in the investigation of the morphology of the color-magnitude diagram of Galactic globular clusters, and the fine-tuning of theoretical models, made possible by the recent observational efforts to build…

Blue horizontal branch and UV bright stars in several globular clusters are analysed spectroscopically and the results are compared with predictions of stellar evolutionary theory. We find that the distribution of temperatures and surface…

Isochrone computations and horizontal branch (HB) models for Y(MS)=0.23 and two values of Z (0.0001, 0.0004)are used to derive constraints on the age indicators and HB morphology of metal-poor clusters with age t (in Gyrs) in the range of…

We present new UV (F218W) data for stars in the central region of the Galactic globular cluster NGC2808, collected with the WFPC2 camera on board of the Hubble Space Telescope. These data together with F439W and F555W-band data and previous…

We study the environmental dependence of color, stellar mass, and morphology by comparing galaxies in a forming cluster to those in the field at z = 1:6 with Hubble Space Telescope near-infrared imaging in the CANDELS/UDS field. We quantify…

We analyse complementary HST and SUBARU data for the globular cluster NGC 2419. We make a detailed analysis of the horizontal branch (HB), that appears composed by two main groups of stars: the luminous blue HB stars ---that extend by…