Peeking beneath the precision floor -- II. Probing the chemo-dynamical histories of the potential globular cluster siblings, NGC 288 and NGC 362
Date Issued
2023
Author(s)
Monty, Stephanie
•
Yong, David
•
•
McKenzie, Madeleine
•
Myeong, GyuChul
•
Buder, Sven
•
Karakas, Amanda I.
•
Freeman, Ken C.
•
•
Belokurov, Vasily
•
Evans, N. Wyn
Abstract
The assembly history of the Milky Way (MW) is a rapidly evolving subject,
with numerous small accretion events and at least one major merger proposed in
the MW's history. Accreted alongside these dwarf galaxies are globular clusters
(GCs), which act as spatially coherent remnants of these past events. Using
high precision differential abundance measurements from our recently published
study, we investigate the likelihood that the MW clusters NGC 362 and NGC 288
are galactic siblings, accreted as part of the Gaia-Sausage-Enceladus (GSE)
merger. To do this, we compare the two GCs at the 0.01 dex level for 20+
elements for the first time. Strong similarities are found, with the two
showing chemical similarity on the same order as those seen between the three
LMC GCs, NGC 1786, NGC 2210 and NGC 2257. However, when comparing GC abundances
directly to GSE stars, marked differences are observed. NGC 362 shows good
agreement with GSE stars in the ratio of Eu to Mg and Si, as well as a clear
dominance in the r- compared to the s-process, while NGC 288 exhibits only a
slight r-process dominance. When fitting the two GC abundances with a GSE-like
galactic chemical evolution model, NGC 362 shows agreement with both the model
predictions and GSE abundance ratios (considering Si, Ni, Ba and Eu) at the
same metallicity. This is not the case for NGC 288. We propose that the two are
either not galactic siblings, or GSE was chemically inhomogeneous enough to
birth two similar, but not identical clusters with distinct chemistry relative
to constituent stars.
Volume
522
Issue
3
Start page
4404
Issn Identifier
0035-8711
Rights
open.access
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