Discovery of 18 stars with -3.10 < [Fe/H] < -1.45 in the Sagittarius dwarf galaxy

Abstract

Studies of the early chemical evolution of some larger dwarf galaxies ( $>10^7$ solar masses) are limited by the small number of stars known at low metallicities in these systems. Here we present metallicities and carbon abundances for eighteen stars with metallicities between $-3.08\le \text{[Fe/H]}\le -1.47$ in the Sagittarius dwarf spheroidal galaxy, using medium-resolution spectra from the MagE spectrograph on the Magellan-Baade Telescope. This sample more than doubles the number of known very metal-poor stars ([Fe/H] $\le -2.0$) in the Sagittarius dwarf galaxy, and identifies one of the first known extremely metal-poor stars ([Fe/H] $\le -3.0$) in the system. These stars were identified as likely metal-poor members of Sagittarius using public, metallicity-sensitive photometry from SkyMapper DR1.1 and proper motion data from Gaia DR2, demonstrating that this dearth of metal-poor stars in some dwarf galaxies can be addressed with targeted searches using public data. We find that none of the stars in our sample are enhanced in carbon, in contrast to the relative prevalence of such stars in the Milky Way halo. Subsequent high-resolution spectroscopy of these stars would be key in detailing the early chemical evolution of the system.

13 pages, 7 figures, 3 tables; Accepted for publication in ApJ

References in corpus (23)

• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• The Dartmouth Stellar Evolution Database
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Carbon-Enhanced Metal-Poor Star Frequencies in the Galaxy: Corrections for the Effect of Evolutionary Status on Carbon Abundances
• CH in stellar atmospheres: an extensive linelist
• SkyMapper Southern Survey: Second Data Release (DR2)
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• The Chemical Evolution of the Draco Dwarf Spheroidal Galaxy
• New Rare Earth Element Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars
• The MagE Spectrograph
• Line lists for the A2PI-X2Sigma+ (red) and {B2Sigma+-X2Sigma} (violet) Systems of CN, 13C14N, and 12C15N, and Application to Astronomical Spectra
• The last breath of the Sagittarius dSph
• Bayesian analysis of resolved stellar spectra: application to MMT/Hectochelle Observations of the Draco dwarf spheroidal
• Detailed Abundances of Two Very Metal-Poor Stars in Dwarf Galaxies
• Carbon in Red Giants in Globular Clusters and Dwarf Spheroidal Galaxies
• Chemical abundances in the nucleus of the Sagittarius dwarf spheroidal galaxy
• Chemical Signatures of the First Supernovae in the Sculptor Dwarf Spheroidal Galaxy
• Distance to the Sagittarius Dwarf Galaxy using MACHO Project RR Lyrae stars
• An inefficient dwarf: Chemical abundances and the evolution of the Ursa Minor dwarf spheroidal galaxy
• Stellar metallicities from SkyMapper photometry I: A study of the Tucana II ultra-faint dwarf galaxy
• Chemical abundance analysis of extremely metal-poor stars in the Sextans dwarf spheroidal galaxy
• Four Metal-poor Stars in the Sagittarius Dwarf Spheroidal Galaxy

Cited by in corpus (9)

• Beyond spectroscopy. I. Metallicities, distances, and age estimates for over twenty million stars from SMSS DR2 and Gaia EDR3
• Detailed chemical abundances of stars in the outskirts of the Tucana II ultra-faint dwarf galaxy
• The chemical abundance pattern of the extremely metal-poor thin disk star 2MASS J1808-5104 and its origins
• Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ($[Fe/H]\lesssim -3$) Regime
• Enrichment by Extragalactic First Stars in the Large Magellanic Cloud
• Extending the Chemical Reach of the H3 Survey: Detailed Abundances of the Dwarf-galaxy Stellar Stream Wukong/LMS-1
• The Pristine Inner Galaxy Survey (PIGS) IV: A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy
• The Pristine Inner Galaxy Survey (PIGS) X. Probing the early chemical evolution of the Sagittarius dwarf galaxy with carbon abundances
• The Pristine Inner Galaxy Survey (PIGS) IX. The largest detailed chemical analysis of very metal-poor stars in the Sagittarius dwarf galaxy