Chemical abundance analysis of three α-poor, metal-poor stars in the ultrafaint dwarf galaxy Horologium I

• Autor(a) principal: Nagasawa, Daniel Q.
• Data de Publicação: 2018
• Outros Autores: Santiago, Basilio Xavier, Yanny, Brian
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRGS
• Texto Completo: http://hdl.handle.net/10183/178349
• topic: Galáxias; Composicao estelar; Metalicidade; Nucleosíntese; Grande Nuvem de Magalhães; Galaxies: abundances; Galaxies: dwarf; Stars: abundances; Stars: chemically peculiar; Supporting material: machine-readable table

We present chemical abundance measurements of three stars in the ultrafaint dwarf galaxy Horologium I, a Milky Way satellite discovered by the Dark Energy Survey. Using high-resolution spectroscopic observations, we measure the metallicity of the three stars, as well as abundance ratios of several α-elements, iron-peak elements, and neutron-capture elements. The abundance pattern is relatively consistent among all three stars, which have a low average metallicity of [Fe/H]∼−2.6 and are not α-enhanced ([α/Fe]∼0.0). This result is unexpected when compared to other low-metallicity stars in the Galactic halo and other ultrafaint dwarfs and suggests the possibility of a different mechanism for the enrichment of Hor I compared to other satellites. We discuss possible scenarios that could lead to this observed nucleosynthetic signature, including extended star formation, enrichment by a Population III supernova, and or an association with the Large Magellanic Cloud.