Kavli Affiliate: Alexander P. Ji
| First 5 Authors: Guilherme Limberg, Alexander P. Ji, Rohan P. Naidu, Anirudh Chiti, Silvia Rossi
| Summary:
We present the first detailed chemical-abundance analysis of stars from the
dwarf-galaxy stellar stream Wukong/LMS-1 covering a wide metallicity range
($-3.5 < rm[Fe/H] lesssim -1.3$). We find abundance patterns that are
effectively indistinguishable from the bulk of Indus and Jhelum, a pair of
smaller stellar streams proposed to be dynamically associated with
Wukong/LMS-1. We confirmed a carbon-enhanced metal-poor star ($rm[C/Fe] >
+0.7$ and $rm[Fe/H] sim -2.9$) in Wukong/LMS-1 with strong enhancements in
Sr, Y, and Zr, which is peculiar given its solar-level [Ba/Fe]. Wukong/LMS-1
stars have high abundances of $alpha$ elements up to $rm[Fe/H] gtrsim -2$,
which is expected for relatively massive dwarfs. Towards the high-metallicity
end, Wukong/LMS-1 becomes $alpha$-poor, revealing that it probably experienced
fairly standard chemical evolution. We identified a pair of N- and Na-rich
stars in Wukong/LMS-1, reminiscent of multiple populations in globular
clusters. This indicates that this dwarf galaxy contained at least one globular
cluster that was completely disrupted in addition to two intact ones previously
known to be associated with Wukong/LMS-1, which is possibly connected to
similar evidence found in Indus. From these $geq$3 globular clusters, we
estimate the total mass of Wukong/LMS-1 to be ${approx}10^{10} M_odot$,
representing ${sim}1$% of the present-day Milky Way. Finally, the [Eu/Mg]
ratio in Wukong/LMS-1 continuously increases with metallicity, making this the
first example of a dwarf galaxy where the production of $r$-process elements is
clearly dominated by delayed sources, presumably neutron-star mergers.
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