”not Too Old” Metal Deficient Stellar Populations: the Case of Metallicity
نویسندگان
چکیده
We investigate the evolution of metal deficient stellar structures, presenting H-burning isochrones covering cluster ages from 800 Myr to 7 Gyr. Evolutionary evidences for selection effects in the metallicity distribution of very metal poor H-burning red giants are reported. The evolution of stars during central and shell He burning is further investigated, discussing the occurrence of He burning pulsators as a function of cluster age.
منابع مشابه
Stellar Populations in the Central Galaxies of Fossil Groups
It is inferred from the symmetrical and luminous X-ray emission of fossil groups that they are mature, relaxed galaxy systems. Cosmological simulations and observations focusing on their dark halo and inter-galactic medium properties confirm their early formation. Recent photometric observations suggest that, unlike the majority of non-fossil brightest group galaxies (BGGs), the central early-t...
متن کاملIntermediate-age metal deficient stellar populations: the case of metallicity Z=0.00001 S.Cassisi1,2, M. Castellani3, and V.Castellani1,4
We investigate the evolution of metal deficient stars, presentingH-burning isochrones covering cluster ages from800 Myr to 7 Gyr. Evolutionary evidences for selection effects in the metallicity distribution of very metal poor H-burning red giants are reported. The evolution of stars during central and shell He burning is further investigated, discussing the occurrence of He burning pulsators as...
متن کاملMetallicity Estimates for Old Star Clusters in M 33
Using the theoretical stellar population synthesis models of BC96, Kong et al. (2003) showed that some BATC colors and color indices could be used to disentangle the age and metallicity effect. They found that there is a very good relation between the flux ratio of L8510/L9170 and the metallicity for stellar populations older than 1 Gyr. In this paper, based on the Kong et al. results and on th...
متن کاملSpectroscopic and photometric studies of low - metallicity star - forming dwarf galaxies . III . SBS 1415 + 437
We present a detailed optical spectroscopic and B, V , I , Hα photometric study of the metal-deficient cometary blue compact dwarf (BCD) galaxy SBS 1415+437. We derive an oxygen abundance 12 + log(O/H) = 7.61±0.01 and 7.62±0.03 (Z = Z⊙/20) ⋆ in the two brightest H ii regions, among the lowest in BCDs. The helium mass fractions in these regions are Y = 0.246±0.003 and 0.243±0.010. Four technique...
متن کاملColour Pairs for Constraining the Age and Metallicity of Stellar Populations
Using a widely used stellar population synthesis model, we study the ability of using pairs of AB system colours to break the well-known stellar age–metallicity degeneracy and give constraints on two luminosity-weighted stellar-population parameters (age and metallicity). The relative age and metallicity sensitivities of AB system colours that relate to u, B, g, V , r, R, i, I, z, J , H , and K...
متن کامل