Investigation of the Puzzling Abundance Pattern in the Stars of the Fornax Dwarf Spheroidal Galaxy

Abstract

Many works have found unusual characteristics of elemental abundances in nearby dwarf galaxies. This implies that there is a key factor of galactic evolution that is different from that of the Milky Way (MW). The chemical abundances of the stars in the Fornax dwarf spheroidal galaxy (Fornax dSph) provide excellent information for setting constraints on the models of the galactic chemical evolution. In this work, adopting the five-component approach, we fit the abundances of the Fornax dSph stars, including $\alpha$ elements, iron group elements and neutron-capture elements. For most sample stars, the relative contributions from the various processes to the elemental abundances are not usually in the MW proportions. We find that the contributions from massive stars to the primary $\alpha$ elements and iron group elements increase monotonously with increasing [Fe/H]. This means that the effect of the galactic wind is not strong enough to halt star formation and the contributions from massive stars to $\alpha$ elements did not halted for [Fe/H]$\lesssim$-0.5. The average contributed ratios of various processes between the dSph stars and the MW stars monotonously decrease with increasing progenitor mass. This is important evidence of a bottom-heavy initial mass function (IMF) for the Fonax dSph, compared to the MW. Considering a bottom-heavy IMF for the dSph, the observed relations of [$\alpha$/Fe] versus [Fe/H], [iron group/Fe] versus [Fe/H] and [neutron-capture/Fe] versus [Fe/H] for the dSph stars can be explained.

38 pages, 11 figures, 2 tables. Accepted for publication in ApJ

References in corpus (10)

• Galactic chemical evolution: Carbon through Zinc
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Cited by in corpus (10)

• Heating efficiency in hydrogen-dominated upper atmospheres
• The galaxy-wide IMF of dwarf late-type to massive early-type galaxies
• VLT/FLAMES spectroscopy of red giant branch stars in the Fornax dwarf spheroidal galaxy
• Thermal mass loss of protoplanetary cores with hydrogen-dominated atmospheres: The influences of ionization and orbital distance
• A New Chemical Evolution Model for Dwarf Spheroidal Galaxies based on Observed Long Star Formation Histories
• Is Germanium (Ge, Z=32) A Neutron-Capture Element?
• Study of the abundance features of the metal-poor star HD 94028
• Estimating R-Process Yields from Abundances of the Metal-Poor Stars
• Footprints of the weak s-process in the carbon-enhanced metal-poor star ET0097
• Astrophysical Origins for the Unusual Chemical Abundance of the Globular Cluster Palomar 1