Kavli Affiliate: Alexander P. Ji
| First 5 Authors: Vinicius M. Placco, Guilherme Limberg, Anirudh Chiti, Deepthi S. Prabhu, Alexander P. Ji
| Summary:
In this work, we present high-resolution spectroscopic observations for six
metal-poor stars with [Fe/H]<-3 (including one with [Fe/H]<-4), selected using
narrow-band Ca II HK photometry from the DECam MAGIC Survey. The spectroscopic
data confirms the accuracy of the photometric metallicities and allows for the
determination of chemical abundances for 16 elements, from carbon to barium.
The program stars have chemical abundances consistent with this metallicity
range. A kinematic/dynamical analysis suggests that all program stars belong to
the distant Milky Way halo population (heliocentric distances 35 < dhelio/kpc <
55), including three with high-energy orbits that might have been associated
with the Magellanic system and one, J0026-5445, having parameters consistent
with being a member of the Sagittarius stream. The remaining two stars show
kinematics consistent with the Gaia-Sausage/Enceladus dwarf galaxy merger.
J0433-5548, with [Fe/H]=-4.12, is a carbon-enhanced ultra metal-poor star, with
[C/Fe]=+1.73. This star is believed to be a bona fide second-generation star,
and its chemical abundance pattern was compared with yields from metal-free
supernova models. Results suggest that J0433-5548 could have been formed from a
gas cloud enriched by a single supernova explosion from a ~11Mo star in the
early universe. The successful identification of such objects demonstrates the
reliability of photometric metallicity estimates, which can be used for target
selection and statistical studies of faint targets in the Milky Way and its
satellite population. These discoveries illustrate the power of measuring
chemical abundances of metal-poor Milky Way halo stars to learn more about
early galaxy formation and evolution.
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