相关论文: Effects of Helium Enrichment in Globular Clusters …

We exploit multi-band Hubble Space Telescope photometry to investigate multiple populations (MPs) along the red horizontal branches (HBs) and red clumps of fourteen metal-rich Globular Clusters (GCs), including twelve Milky Way GCs and the…

The detection of star-to-star chemical variations in star clusters older than 2 Gyr has changed the traditional view of star clusters as canonical examples of "simple stellar populations" (SSPs) into the so-called "multiple stellar…

Globular clusters (GCs) are the oldest stellar systems in the Milky Way. Long time considered as simple stellar populations, nowadays we recognize their complex star formation history through precise abundance analysis of a variety of…

Globular clusters (GCs) are fundamental for understanding the integrated light of old stellar populations and galaxy assembly processes. However, the role of hot, evolved stars, such as horizontal branch (HB), extreme HB, and blue…

We present cosmological hydrodynamical simulations of galaxy clusters aimed at studying the process of metal enrichment of the intra--cluster medium (ICM). These simulations have been performed by implementing a detailed model of chemical…

Integrated light from distant galaxies is often compared to stellar population models via the equivalent widths of spectral features--spectral indices--whose strengths rely on the abundances of one or more elements. Such comparisons hinge…

Core helium burning is the dominant source of energy of extreme horizontal branch stars, as the hydrogen envelope is too small to contribute to the nuclear energy output. The evolution of each mass in the HR diagram occurs along vertical…

We present a chemical abundance study of three inner old halo clusters NGC 6287, NGC 6293, and NGC 6541, finding [Fe/H] = -2.01 +/- 0.05, -1.99 +/- 0.02, and -1.76 +/- 0.02, respectively, and our metallicity measurements are in good…

We present abundances of globular clusters in the Milky Way and Fornax from integrated light spectra. Our goal is to evaluate the consistency of the integrated light analysis relative to standard abundance analysis for individual stars in…

The Horizontal Branch (HB) second parameter of Globular Clusters (GCs) is a major open issue in stellar evolution. Large photometric and spectroscopic databases allow a re-examination of this issue. We derive median and extreme (90% of the…

We present a CCD investigation of the galactic globular M5 aimed to increase the statistical relevance of the available sample of evolving bright stars. Previous investigations, limited to the outer cluster region, have been extended toward…

The spectroscopic and photometric signals of the star-to-star abundance variations found in globular clusters seem to be correlated with global parameters like the cluster's metallicity, mass and age. Understanding this behaviour could…

We analyse the population of bright star clusters in the interacting galaxy pair NGC 4038/39 detected with HST WFPC1 by Whitmore & Schweizer (1995) using our spectrophotometric evolutionary synthesis models for various initial…

We have observed the CN features at $\sim$3800 ~\AA~ and 4120~ \AA~ as well as the CH band at $\sim$4300~\AA~ for 145 evolved stars in the Galactic globular cluster M71 using the multi-object spectrograph, Hydra, on the WIYN-3.5m telescope.…

We present a new grid of stellar models and isochrones for old stellar populations, covering a large range of [Fe/H] values, for an heavy element mixture characterized by CNONa abundance anticorrelations as observed in Galactic globular…

The double main sequence identified in the globular cluster Omega Centauri has been interpreted using isochrones to indicate a large variation in the abundance of helium. If true, a helium enhancement carries strong implications for the…

Multiple populations are ubiquitous in the old massive globular clusters (GCs) of the Milky Way. It is still unclear how they arose during the formation of a GC. The topic of iron and metallicity variations has recently attracted attention…

In this study we present first results from multi-wavelength Hubble Space Telescope (HST) observations of the Galactic globular cluster GC NGC2808 as an extension of the Hubble Space Telescope UV Legacy Survey of Galactic GCs (GO-13297 and…

Once fixed the age and metallicity; the colour distribution of horizontal branch stars in a globular cluster depends on few parameters: the helium abundance of the population and the mass lost during the pre-HB stages. These parameters are…

The "chromosome maps" (ChMs) of globular clusters (GCs) have revealed that these ancient structures are not homogeneous in metallicity in various ways, and in different natures. The Type II GCs generally display larger variations, sometimes…