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Title: The universal stellar mass-stellar metallicity relation for dwarf galaxies

We present spectroscopic metallicities of individual stars in seven gas-rich dwarf irregular galaxies (dIrrs), and we show that dIrrs obey the same mass-metallicity relation as the dwarf spheroidal (dSph) satellites of both the Milky Way and M31: Z{sub ∗}∝M{sub ∗}{sup 0.30±0.02}. The uniformity of the relation is in contradiction to previous estimates of metallicity based on photometry. This relationship is roughly continuous with the stellar mass-stellar metallicity relation for galaxies as massive as M {sub *} = 10{sup 12} M {sub ☉}. Although the average metallicities of dwarf galaxies depend only on stellar mass, the shapes of their metallicity distributions depend on galaxy type. The metallicity distributions of dIrrs resemble simple, leaky box chemical evolution models, whereas dSphs require an additional parameter, such as gas accretion, to explain the shapes of their metallicity distributions. Furthermore, the metallicity distributions of the more luminous dSphs have sharp, metal-rich cut-offs that are consistent with the sudden truncation of star formation due to ram pressure stripping.
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. University of California, Department of Physics and Astronomy, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States)
  2. California Institute of Technology, Department of Astronomy and Astrophysics, 1200 E. California Blvd., MC 249-17, Pasadena, CA 91125 (United States)
  3. UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
  4. The Harker School, 500 Saratoga Ave., San Jose, CA 95117 (United States)
  5. INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy)
Publication Date:
OSTI Identifier:
22348465
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; DISTRIBUTION; DWARF STARS; GALAXIES; MASS; METALLICITY; METALS; MILKY WAY; PHOTOMETRY; SATELLITES; STARS; STRIPPING