Kavli Affiliate: Alexander P. Ji
| First 5 Authors: Terese T. Hansen, Joshua D. Simon, Ting S. Li, Domani Sharkey, Alexander P. Ji
| Summary:
The growing number of Milky Way satellites detected in recent years has
introduced a new focus for stellar abundance analysis. Abundances of stars in
satellites have been used to probe the nature of these systems and their
chemical evolution. However, for most satellites, only centrally located stars
have been examined. This paper presents an analysis of three stars in the
Tucana V system, one in the inner region and two at $sim$10arcmin (7–10
half-light radii) from the center. We find a remarkable chemical diversity
between the stars. One star exhibits enhancements in rapid neutron-capture
elements (an $r$-I star), and another is highly enhanced in C, N, and O but
with low neutron-capture abundances (a CEMP-no star). The metallicities of the
stars analyzed span more than 1~dex from $mathrm{[Fe/H]}=-3.55$ to $-2.46$.
This, combined with a large abundance range of other elements like Ca, Sc, and
Ni, confirms that Tuc~V is an ultra-faint dwarf (UFD) galaxy. The variation in
abundances, highlighted by [Mg/Ca] ratios ranging from $+0.89$ to $-0.75$,
among the stars, demonstrates that the chemical enrichment history of Tuc~V was
very inhomogeneous. Tuc~V is only the second UFD galaxy in which stars located
at large distances from the galactic center have been analyzed, along with
Tucana~II. The chemical diversity seen in these two galaxies, driven by the
composition of the non-central member stars, suggests that distant member stars
are important to include when classifying faint satellites and that these
systems may have experienced more complex chemical enrichment histories than
previously anticipated.
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