Evidence for C, O, Al and Mg variations in the GD-1 stellar stream. (arXiv:2111.12626v1 [astro-ph.GA])

Evidence for C, O, Al and Mg variations in the GD-1 stellar stream. (arXiv:2111.12626v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Balbinot_E/0/1/0/all/0/1">Eduardo Balbinot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cabrera_Ziri_I/0/1/0/all/0/1">Ivan Cabrera-Ziri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lardo_C/0/1/0/all/0/1">Carmela Lardo</a>

Dynamically cold stellar streams are the relics left over from globular
cluster dissolution. These relics offer a unique insight into a now fully
disrupted population of ancient clusters in our Galaxy. Using a combination of
Gaia eDR3 proper motions, optical and near-UV colours we select a sample of
likely Red Giant Branch stars from the GD-1 stream for medium-low resolution
spectroscopic follow-up. Based on radial velocity and metallicity, we are able
to find 14 new members of GD-1, 5 of which are associated with the emph{spur}
and emph{blob/cocoon} off-stream features. We measured C-abundances to probe
for the abundance variations known to exist in globular clusters. These
variations are expected to manifest in a subtle way in globular clusters with
such low masses ($sim 10^4 {rm ~M _{odot}}$) and metallicities (${rm
[Fe/H]}sim-2.1 {rm ~dex}$). We find that the C-abundances of the stars in our
sample display a small but significant ($ 3sigma$ level) spread. Furthermore,
we find $ge 4sigma$ variations in Al- and Mg-abundances as well as a
$sim2sigma$ O-abundance variation among the stars in our sample that have
been observed by APOGEE. These abundance patterns match the ones found in
Galactic globular clusters of similar metallicity. Our results suggest that
GD-1 represents the first fully disrupted globular cluster where light-element
abundance spreads have been found.

Dynamically cold stellar streams are the relics left over from globular
cluster dissolution. These relics offer a unique insight into a now fully
disrupted population of ancient clusters in our Galaxy. Using a combination of
Gaia eDR3 proper motions, optical and near-UV colours we select a sample of
likely Red Giant Branch stars from the GD-1 stream for medium-low resolution
spectroscopic follow-up. Based on radial velocity and metallicity, we are able
to find 14 new members of GD-1, 5 of which are associated with the emph{spur}
and emph{blob/cocoon} off-stream features. We measured C-abundances to probe
for the abundance variations known to exist in globular clusters. These
variations are expected to manifest in a subtle way in globular clusters with
such low masses ($sim 10^4 {rm ~M _{odot}}$) and metallicities (${rm
[Fe/H]}sim-2.1 {rm ~dex}$). We find that the C-abundances of the stars in our
sample display a small but significant ($ 3sigma$ level) spread. Furthermore,
we find $ge 4sigma$ variations in Al- and Mg-abundances as well as a
$sim2sigma$ O-abundance variation among the stars in our sample that have
been observed by APOGEE. These abundance patterns match the ones found in
Galactic globular clusters of similar metallicity. Our results suggest that
GD-1 represents the first fully disrupted globular cluster where light-element
abundance spreads have been found.

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