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Effect of increasing helium content and disk dwarfs evolution on the chemical enrichment of the galaxy

Abstract

The author deals with two main effects: First the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood, and second, the theoretical possibility of (i) an increased helium content as the Galaxy evolves, and (ii) the presence of evolutionary effects in disk dwarfs (i.e., the age of some or all stars considered up to the subgiant phase is not necessarily longer than the age of the galactic disk). Account is taken of a linear increase of helium content with metal content, and some constraints are imposed relative to initial, solar and present-day observed values of Y and Z, and to observed relative helium to heavy element enrichment, ..delta..Y/..delta..Z. In this way, little influence is found on the empirical metal abundance distribution in the range 0<=..delta..Y/..delta..Z<=3, while larger values of ..delta..Y/..delta..Zwould lead to a more significant influence. 'Evolved' and 'unevolved' theoretical metal abundance distributions are derived by accounting for a two-phase model of chemical evolution of galaxies and for a linear mass dependence of star lifetimes in the spectral range G2V-G8V and are compared with the empirical distribution. All are in satisfactory agreement due to systematic shift data by different observations; several values of collapse time Tsub(c)  More>>
Authors:
Caimmi, R [1] 
  1. Padua Univ. (Italy). Ist. di Astronomia
Publication Date:
Jul 01, 1979
Product Type:
Journal Article
Reference Number:
AIX-11-495674; EDB-80-063289
Resource Relation:
Journal Name: Astrophys. Space Sci.; (Netherlands); Journal Volume: 63:2
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DWARF STARS; GALACTIC EVOLUTION; MILKY WAY; CHEMICAL COMPOSITION; HELIUM; MAIN SEQUENCE STARS; MASS; METALS; STAR EVOLUTION; STAR MODELS; CRYOGENIC FLUIDS; ELEMENTS; FLUIDS; GALAXIES; MATHEMATICAL MODELS; NONMETALS; RARE GASES; STARS; 640105* - Astrophysics & Cosmology- Galaxies; 640102 - Astrophysics & Cosmology- Stars & Quasi-Stellar, Radio & X-Ray Sources
OSTI ID:
5499219
Country of Origin:
Netherlands
Language:
English
Other Identifying Numbers:
Journal ID: CODEN: APSSB
Submitting Site:
INIS
Size:
Pages: 389-403
Announcement Date:

Citation Formats

Caimmi, R. Effect of increasing helium content and disk dwarfs evolution on the chemical enrichment of the galaxy. Netherlands: N. p., 1979. Web. doi:10.1007/BF00638910.
Caimmi, R. Effect of increasing helium content and disk dwarfs evolution on the chemical enrichment of the galaxy. Netherlands. doi:10.1007/BF00638910.
Caimmi, R. 1979. "Effect of increasing helium content and disk dwarfs evolution on the chemical enrichment of the galaxy." Netherlands. doi:10.1007/BF00638910. https://www.osti.gov/servlets/purl/10.1007/BF00638910.
@misc{etde_5499219,
title = {Effect of increasing helium content and disk dwarfs evolution on the chemical enrichment of the galaxy}
author = {Caimmi, R}
abstractNote = {The author deals with two main effects: First the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood, and second, the theoretical possibility of (i) an increased helium content as the Galaxy evolves, and (ii) the presence of evolutionary effects in disk dwarfs (i.e., the age of some or all stars considered up to the subgiant phase is not necessarily longer than the age of the galactic disk). Account is taken of a linear increase of helium content with metal content, and some constraints are imposed relative to initial, solar and present-day observed values of Y and Z, and to observed relative helium to heavy element enrichment, ..delta..Y/..delta..Z. In this way, little influence is found on the empirical metal abundance distribution in the range 0<=..delta..Y/..delta..Z<=3, while larger values of ..delta..Y/..delta..Zwould lead to a more significant influence. 'Evolved' and 'unevolved' theoretical metal abundance distributions are derived by accounting for a two-phase model of chemical evolution of galaxies and for a linear mass dependence of star lifetimes in the spectral range G2V-G8V and are compared with the empirical distribution. All are in satisfactory agreement due to systematic shift data by different observations; several values of collapse time Tsub(c) and age of the Galaxy T are also considered. Finally, models of chemical evolution invoking homogeneous collapse without infall and inhomogeneous collapse with infall, are briefly discussed relative to the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood.}
doi = {10.1007/BF00638910}
journal = {Astrophys. Space Sci.; (Netherlands)}
volume = {63:2}
journal type = {AC}
place = {Netherlands}
year = {1979}
month = {Jul}
}