The extended 'stellar halo' of the Ursa Minor dwarf galaxy - Galaxies, Etoiles, Physique, Instrumentation
Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2023

The extended 'stellar halo' of the Ursa Minor dwarf galaxy

Federico Sestito
  • Fonction : Auteur
Daria Zaremba
  • Fonction : Auteur
Kim A. Venn
  • Fonction : Auteur
Lina d'Aoust
  • Fonction : Auteur
Christian Hayes
  • Fonction : Auteur
Jaclyn Jensen
  • Fonction : Auteur
Julio F. Navarro
  • Fonction : Auteur
Emma Fernández-Alvar
  • Fonction : Auteur
Jennifer Glover
  • Fonction : Auteur
Alan W. Mcconnachie
  • Fonction : Auteur
André-Nicolas Chené
  • Fonction : Auteur

Résumé

Stellar candidates in the Ursa Minor (UMi) dwarf galaxy have been found using a new Bayesian algorithm applied to Gaia EDR3 data. Five of these targets are located in the extreme outskirts of UMi, from ~5 to 12 elliptical half-light radii (rh), where rh(UMi) = 17.32 ± 0.11 arcmin, and have been observed with the high-resolution Gemini Remote Access to CFHT ESPaDOnS Spectrograph at the Gemini North telescope. Precise radial velocities (σRV < 2 km s-1) and metallicities ($\sigma _{\rm {{\rm [Fe/H]}}}\ \ 0.2$ dex) confirm their memberships of UMi. Detailed analysis of the brightest and outermost star (Target 1, at ~12rh), yields precision chemical abundances for the α (Mg, Ca, and Ti), odd-Z (Na, K, and Sc), Fe-peak (Fe, Ni, and Cr), and neutron-capture (Ba) elements. With data from the literature and APOGEE data release 17, we find the chemical patterns in UMi are consistent with an outside-in star-formation history that includes yields from core-collapse supernovae, asymptotic giant branch stars, and Type Ia supernovae. Evidence for a knee in the [α/Fe] ratios near [Fe/H] ~ -2.1 indicates a low star-formation efficiency similar to that in other dwarf galaxies. Detailed analysis of the surface number density profile shows evidence that UMi's outskirts have been populated by tidal effects, likely as a result of completing multiple orbits around the Galaxy.
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insu-04848713 , version 1 (20-12-2024)

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Federico Sestito, Daria Zaremba, Kim A. Venn, Lina d'Aoust, Christian Hayes, et al.. The extended 'stellar halo' of the Ursa Minor dwarf galaxy. Monthly Notices of the Royal Astronomical Society, 2023, 525, pp.2875-2890. ⟨10.1093/mnras/stad2427⟩. ⟨insu-04848713⟩
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