Implications of Elemental Abundances in Dwarf Spheroidal Galaxies

Abstract

Unusual elemental abundance patterns observed for stars belonging to nearby dwarf spheroidal (dSph) galaxies are discussed. Analysis of the [alpha/H] vs. [Fe/H] diagrams where alpha represents Mg or average of alpha-elements reveals that Fe from Type Ia supernovae (SNe Ia) does not contribute to the stellar abundances in the dSph galaxies where the member stars exhibit low alpha/Fe ratios except for the most massive dSph galaxy, the Sagitarrius. The more massive dwarf (irregular) galaxy, the Large Magellanic Cloud, also have an SNe Ia signature in the stellar abundances. These findings suggest that the condition of whether SNe Ia contribute to chemical evolution in dwarf galaxies is likely to depend on the mass scale of galaxies. Unusual Mg abundances in some dSph stars are also found to be the origin of the large scatter in the [Mg/Fe] ratios and responsible for a seemingly decreasing [Mg/Fe] feature with increasing [Fe/H]. In addition, the lack of massive stars in the dSph galaxies does not satisfactorily account for the low-alpha signature. Considering the assemblage of deficient elements (O, Mg, Si, Ca, Ti, and Zn), all of which are synthesized in pre-SN massive stars and in SN explosions, the low-alpha signature appears to reflect the heavy-element yields of massive stars with smaller rotation compared to solar neighborhood stars.

7 pages, 4 figures, accepted by A&A

References in corpus (11)

• Stellar Chemical Signatures And Hierarchical Galaxy Formation
• Two distinct ancient components in the Sculptor Dwarf Spheroidal Galaxy: First Results from DART
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: IV. Modeling the Sagittarius Tidal Tails
• Stellar evolution with rotation XII: Pre-supernova models
• Lambda-Cold Dark Matter, Stellar Feedback, and the Galactic Halo Abundance Pattern
• 'Sculptor'-ing the Galaxy? The Chemical Compositions of Red Giants in the Sculptor Dwarf Spheroidal Galaxy
• Impact of Reionization on the Stellar Populations of Nearby Dwarf Galaxies
• The Ital-FLAMES survey of the Sagittarius dwarf Spheroidal galaxy. I. Chemical abundances of bright RGB stars
• Yields of rotating stars at solar metallicity
• The [Zn/Fe] -- [Fe/H] trend for disk and halo stars
• Effects of Metallicity on the Rotation Rates of Massive Stars

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• Astrophysics in 2006
• The Origin of the Metal-Poor Common Proper Motion Pair HD 134439/134440: Insights from New Elemental Abundances