Linking the metallicity distribution of Galactic halo stars to the enrichment history of the universe

Evan Scannapieco, Tom Broadhurst

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

We compare the metallicity distribution of Galactic halo stars with three-dimensional realizations of hierarchical galaxy formation. Outflows from dwarf galaxies enrich the intergalactic medium inhomogeneously, at a rate depending on the local galaxy density. Consequently, the first stars created in small early-forming galaxies are less metal-rich than the first stars formed in more massive galaxies, which typically form later. As most halo stars are likely to originate in accreted dwarfs, while disk stars formed out of outflow-enriched gas, this scenario naturally generates a "metallicity floor" for old disk stars, which we find to be roughly coincident with the higher end of our predicted metallicity distribution of halo stars, in agreement with observations. The broad and centrally peaked distribution of halo star metallicities is well reproduced in our models, with a natural dispersion depending on the exact accretion history. Our modeling includes the important "baryonic stripping" effect of early outflows, which brush away the tenuously held gas in neighboring previrialized density perturbations. This stripping process does not significantly modify the predicted shape of the halo star metal distribution but inhibits star formation and hence the number of accreted stars, helping to reconcile our model with the observed total Galactic halo luminosity and the lack of low-luminosity local dwarf galaxies relative to N-body predictions.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume550
Issue number1 PART 2
DOIs
StatePublished - Mar 20 2001
Externally publishedYes

Fingerprint

galactic halos
metallicity
universe
histories
stars
outflow
history
halos
metal
gas
dwarf galaxies
galaxies
stripping
accretion
perturbation
luminosity
distribution
prediction
intergalactic media
modeling

Keywords

  • Cosmology: theory
  • Galaxies: dwarf
  • Galaxy: formation
  • Galaxy: halo
  • Intergalactic medium

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Linking the metallicity distribution of Galactic halo stars to the enrichment history of the universe. / Scannapieco, Evan; Broadhurst, Tom.

In: Astrophysical Journal, Vol. 550, No. 1 PART 2, 20.03.2001.

Research output: Contribution to journalArticle

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AB - We compare the metallicity distribution of Galactic halo stars with three-dimensional realizations of hierarchical galaxy formation. Outflows from dwarf galaxies enrich the intergalactic medium inhomogeneously, at a rate depending on the local galaxy density. Consequently, the first stars created in small early-forming galaxies are less metal-rich than the first stars formed in more massive galaxies, which typically form later. As most halo stars are likely to originate in accreted dwarfs, while disk stars formed out of outflow-enriched gas, this scenario naturally generates a "metallicity floor" for old disk stars, which we find to be roughly coincident with the higher end of our predicted metallicity distribution of halo stars, in agreement with observations. The broad and centrally peaked distribution of halo star metallicities is well reproduced in our models, with a natural dispersion depending on the exact accretion history. Our modeling includes the important "baryonic stripping" effect of early outflows, which brush away the tenuously held gas in neighboring previrialized density perturbations. This stripping process does not significantly modify the predicted shape of the halo star metal distribution but inhibits star formation and hence the number of accreted stars, helping to reconcile our model with the observed total Galactic halo luminosity and the lack of low-luminosity local dwarf galaxies relative to N-body predictions.

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KW - Galaxy: halo

KW - Intergalactic medium

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