The COMBS survey I: Chemical Origins of Metal-Poor Stars in the Galactic Bulge. (arXiv:1903.11615v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Lucey_M/0/1/0/all/0/1">Madeline Lucey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hawkins_K/0/1/0/all/0/1">Keith Hawkins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ness_M/0/1/0/all/0/1">Melissa Ness</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Asplund_M/0/1/0/all/0/1">Martin Asplund</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bensby_T/0/1/0/all/0/1">Thomas Bensby</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casagrande_L/0/1/0/all/0/1">Luca Casagrande</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feltzing_S/0/1/0/all/0/1">Sofia Feltzing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Freeman_K/0/1/0/all/0/1">Kenneth C. Freeman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kobayashi_C/0/1/0/all/0/1">Chiaki Kobayashi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marino_A/0/1/0/all/0/1">Anna F. Marino</a>
Chemistry and kinematic studies can determine the origins of stellar
population across the Milky Way. The metallicity distribution function of the
bulge indicates that it comprises multiple populations, the more metal-poor end
of which is particularly poorly understood. It is currently unknown if
metal-poor bulge stars ([Fe/H] $<$ -1 dex) are part of the stellar halo in the
inner most region, or a distinct bulge population or a combination of these.
Cosmological simulations also indicate that the metal-poor bulge stars may be
the oldest stars in the Galaxy. In this study, we successfully target
metal-poor bulge stars selected using SkyMapper photometry. We determine the
stellar parameters of 26 stars and their elemental abundances for 22 elements
using R$sim$ 47,000 VLT/UVES spectra and contrast their elemental properties
with that of other Galactic stellar populations. We find that the elemental
abundances we derive for our metal-poor bulge stars have much lower overall
scatter than typically found in the halo. This indicates that these stars may
be a distinct population confined to the bulge. If these stars are,
alternatively, part of the inner-most distribution of the halo, this indicates
that the halo is more chemically homogeneous at small Galactic radii than at
large radii. We also find two stars whose chemistry is consistent with
second-generation globular cluster stars. This paper is the first part of the
Chemical Origins of Metal-poor Bulge Stars (COMBS) survey that will
chemo-dynamically characterize the metal-poor bulge population.
Chemistry and kinematic studies can determine the origins of stellar
population across the Milky Way. The metallicity distribution function of the
bulge indicates that it comprises multiple populations, the more metal-poor end
of which is particularly poorly understood. It is currently unknown if
metal-poor bulge stars ([Fe/H] $<$ -1 dex) are part of the stellar halo in the
inner most region, or a distinct bulge population or a combination of these.
Cosmological simulations also indicate that the metal-poor bulge stars may be
the oldest stars in the Galaxy. In this study, we successfully target
metal-poor bulge stars selected using SkyMapper photometry. We determine the
stellar parameters of 26 stars and their elemental abundances for 22 elements
using R$sim$ 47,000 VLT/UVES spectra and contrast their elemental properties
with that of other Galactic stellar populations. We find that the elemental
abundances we derive for our metal-poor bulge stars have much lower overall
scatter than typically found in the halo. This indicates that these stars may
be a distinct population confined to the bulge. If these stars are,
alternatively, part of the inner-most distribution of the halo, this indicates
that the halo is more chemically homogeneous at small Galactic radii than at
large radii. We also find two stars whose chemistry is consistent with
second-generation globular cluster stars. This paper is the first part of the
Chemical Origins of Metal-poor Bulge Stars (COMBS) survey that will
chemo-dynamically characterize the metal-poor bulge population.
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