A Study of Abundance Patterns in the Sextans and Sculptor Dwarf Spheroidal Galaxies

Abstract

In this work, we employ a multicomponent decomposition model to study the Sextans and Sculptor dwarf spheroidal galaxies, which have distinct evolutionary histories. Sextans exhibits massive stars dominating in the early stages of its evolution and a lower contribution from type Ia supernovae (SNe Ia). With increasing metallicity, the evolution of massive stars in Sextans shows two turning points, at [Fe/H] ∼ −2.8 and [Fe/H] ∼ −2.0, indicating episodes of accretion events and galactic winds during its evolution. In the late stages, influenced by galactic winds, the contribution from massive stars ceases, and SNe Ia become the dominant evolutionary process. Sculptor exhibits contributions from the main r -process, early very massive stars, massive stars, SNe Ia, and asymptotic giant branch (AGB) stars. In its early stages, the contributions from early very massive stars and massive stars are dominant, while the contribution from SNe Ia is low. Around [Fe/H] ∼ −2, the contribution from early very massive stars starts to decline, while the contributions from SNe Ia and massive stars continue to increase. At [Fe/H] ∼ −1.7, the contribution from massive stars gradually decreases and approaches the level of the solar neighborhood, while the contribution from AGB stars continues to rise with increasing metallicity. Both dwarf galaxies exhibit characteristic features of similar initial mass functions, but the Sextans dwarf galaxy exhibits a high-mass cutoff, while the Sculptor dwarf galaxy does not. Additionally, through decomposition, we can analyze the contributions of different astrophysical processes to [ α /Fe] versus [Fe/H], [iron-group/Fe] versus [Fe/H], and [neutron-capture/Fe] versus [Fe/H].

Keywords

• Dwarf spheroidal galaxies
• Astrophysical processes