History of Milky Way Dwarf Spheroidal Galaxies Imprinted on Abundance Patterns of Neutron-Capture Elements

Abstract

Stellar abundance pattern of neutron-capture elements such as barium is used as a powerful tool to infer how star formation proceeded in dwarf spheroidal (dSph) galaxies. It is found that the abundance correlation of barium with iron in stars belonging to dSph galaxies orbiting the Milky Way, i.e., Draco, Sextans, and Ursa Minor have a feature similar to the barium-iron correlation in Galactic metal-poor stars. The common feature of these two correlations can be realized by our inhomogeneous chemical evolution model based on the supernova-driven star formation scenario if dSph stars formed from gas with a velocity dispersion of ~26 km/s. This velocity dispersion together with the stellar luminosities strongly suggest that dark matter dominated dSph galaxies. The tidal force of the Milky Way links this velocity dispersion with the currently observed value <10 km/s by stripping the dark matter in dSph galaxies. As a result, the total mass of each dSph galaxy is found to have been originally ~25 times larger than at present. Our inhomogeneous chemical evolution model succeeds in reproducing the stellar [Fe/H] distribution function observed in Sextans. In this model, supernovae immediately after the end of the star formation epoch can expel the remaining gas over the gravitational potential of the dSph galaxy.

5 pages including 2 figures, to appear in ApJ Letters Vol.571

References in corpus (5)

• Measurement of stellar age from uranium decay
• New insights on the Draco dwarf spheroidal galaxy from SDSS: a larger radius and no tidal tails
• Supernova SN1987A Revisited as a Major Production Site for r-Process Elements
• Analysis of a Proper-Motion Selected Sample of Stars in the Ursa Minor Dwarf Spheroidal Galaxy
• Chemical Evolution of Odd Elements in an Inhomogeneous Early Galaxy

Cited by in corpus (9)

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• Detailed Abundances of Two Very Metal-Poor Stars in Dwarf Galaxies
• The first determination of the actinide Th abundance for a red giant of the Ursa Minor dwarf galaxy
• Galactic Chemical Evolution
• Extreme r-process enhanced stars at high metallicity in Fornax
• Star Formation History of Omega Centauri Imprinted in Elemental Abundance Patterns
• Implications of Elemental Abundances in Dwarf Spheroidal Galaxies
• Accretion of dust grains as a possible origin of metal-poor stars with low alpha/Fe ratios