Effects of Helium Enrichment in Globular Clusters I.Theoretical Plane with PGPUC stellar evolution code

Abstract

Recently, the study of globular cluster (GC) CMDs has shown that some of them harbor multiple populations with different chemical compositions and/or ages. In the first case, the most common candidate is a spread in the initial helium abundance, but this quantity is difficult to determine spectroscopically due to the fact that helium absorption lines are not present in cooler stars, whereas for hotter GC stars gravitational settling of helium becomes important. As a consequence, indirect methods to determine the initial Y among populations are necessary. For that reason, in this series of papers, we investigate the effects of a Y enrichment in populations covering the range of GC metallicities. In this first paper, we present the theoretical evolutionary tracks, isochrones, and ZAHB loci calculated with the Princeton-Goddard-PUC (PGPUC) stellar evolutionary code, which has been updated with the most recent input physics and compared with other theoretical databases. The chemical composition grid covers 9 Z ranging from Z=1.60x10^-4 to 1.57x10^-2, 7 Y from Y=0.230 to 0.370, and an alpha-element enhancement of [alpha/Fe]=0.3. The effects of different helium abundances that can be observed in isochrones are: splits in the MS, differences in the L and Teff of the turn off point, splits in the SGB being more prominent for lower ages or higher metallicities, splits in the lower red giant branch being more prominent for higher ages or higher metallicities, differences in L of the RGB bump (with small changes in Teff), and differences in L at the RGB tip. At the ZAHB, when Y is increased there is an increase of L for low Teff, which is affected in different degrees depending on the age of the GC being studied. Finally, the ZAHB morphology distribution depending on the age explains how for higher GC metallicities a population with higher helium abundance could be hidden at the red ZAHB locus.

18 pages, 15 figures

References in corpus (15)

• The Dartmouth Stellar Evolution Database
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• Scaled solar tracks and isochrones in a large region of the Z-Y plane I. From the ZAMS to the TP-AGB end for 0.15 - 2.5 Mo stars
• The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
• Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters
• The primordial abundance of 4He: a self-consistent empirical analysis of systematic effects in a large sample of low-metallicity HII regions
• The double Subgiant Branch of NGC 1851: the role of the CNO abundance
• Stellar Models with Enhanced Abundances of C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti, in Turn, at Constant Helium and Iron Abundances
• A critical test of empirical mass loss formulae applied to individual giants and supergiants
• On the Use of Blanketed Atmospheres as Boundary Conditions for Stellar Evolutionary Models
• Formation of the Galactic Halo
• Constraints on Helium Enhancement in the Globular Cluster M3 (NGC 5272): The Horizontal Branch Test
• The neutrino emission due to plasmon decay and neutrino luminosity of white dwarfs
• A Semi-Empirical Study of the Mass Distribution of Horizontal Branch Stars in M3 (NGC 5272)

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• Inferring the Helium abundance of extragalactic Globular Clusters using Integrated Spectra
• A Comparative Study Between M30 and M92 : M92 Is A Merger Remnant With A Large Helium Enhancement
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