High Resolution Optical Spectroscopy of Stars in the Sylgr Stellar Stream

Abstract

We observe two metal-poor main sequence stars that are members of the recently-discovered Sylgr stellar stream. We present radial velocities, stellar parameters, and abundances for 13 elements derived from high-resolution optical spectra collected using the Magellan Inamori Kyocera Echelle spectrograph. The two stars have identical compositions (within 0.13 dex or 1.2 sigma) among all elements detected. Both stars are very metal poor ([Fe/H] = -2.92 +/- 0.06). Neither star is highly enhanced in C ([C/Fe] < +1.0). Both stars are enhanced in the alpha elements Mg, Si, and Ca ([alpha/Fe] = +0.32 +/- 0.06), and ratios among Na, Al, and all Fe-group elements are typical for other stars in the halo and ultra-faint and dwarf spheroidal galaxies at this metallicity. Sr is mildly enhanced ([Sr/Fe] = +0.22 +/- 0.11), but Ba is not enhanced ([Ba/Fe] < -0.4), indicating that these stars do not contain high levels of neutron-capture elements. The Li abundances match those found in metal-poor unevolved field stars and globular clusters (log epsilon (Li) = 2.05 +/- 0.07), which implies that environment is not a dominant factor in determining the Li content of metal-poor stars. The chemical compositions of these two stars cannot distinguish whether the progenitor of the Sylgr stream was a dwarf galaxy or a globular cluster. If the progenitor was a dwarf galaxy, the stream may originate from a dense region such as a nuclear star cluster. If the progenitor was a globular cluster, it would be the most metal-poor globular cluster known.

Accepted for publication in the Astrophysical Journal (17 pages, 4 figures, 3 tables)

References in corpus (46)

• The NumPy array: a structure for efficient numerical computation
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Empirical Color Transformations Between SDSS Photometry and Other Photometric Systems
• The SEGUE Stellar Parameter Pipeline. I. Description and Initial Validation Tests
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Near-UV Observations of HD221170: New Insights into the Nature of r-Process-Rich Stars
• Segue 1: An Unevolved Fossil Galaxy from the Early Universe
• First stars VII. Lithium in extremely metal poor dwarfs
• NLTE abundances of Mn in a sample of metal-poor stars
• The Chemical Evolution of the Draco Dwarf Spheroidal Galaxy
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. II. Catalog of Stars in Milky Way Dwarf Satellite Galaxies
• The Highly Unusual Chemical Composition of the Hercules Dwarf Spheroidal Galaxy
• Complete element abundances of nine stars in the r-process galaxy Reticulum II
• Improved Laboratory Transition Probabilities for Neutral Chromium and Re-determination of the Chromium Abundance for the Sun and Three Stars
• The Streams of the Gaping Abyss: A population of entangled stellar streams surrounding the Inner Galaxy
• Detection of Elements at All Three r-process Peaks in the Metal-Poor Star HD 160617
• NLTE determination of the aluminium abundance in a homogeneous sample of extremely metal-poor stars
• An R-process enhanced star in the dwarf galaxy Tucana III
• Characterization and history of the Helmi streams with Gaia DR2
• High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the SkyMapper Survey
• Fe I Oscillator Strengths for the Gaia-ESO Survey
• Modeling the Formation of Globular Cluster Systems in the Virgo Cluster
• Mg line formation in late-type stellar atmospheres: I. The model atom
• Globular cluster number density profiles using Gaia DR2
• Detailed Abundances of Two Very Metal-Poor Stars in Dwarf Galaxies
• Experimental and theoretical oscillator strengths of Mg I for accurate abundance analysis
• Improved V II log($gf$) Values, Hyperfine Structure Constants, and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937
• Chemical Diversity in the Ultra-faint Dwarf Galaxy Tucana II
• NGC 6535: the lowest mass Milky Way globular cluster with a Na-O anti-correlation? Cluster mass and age in the multiple population context
• Chemical Abundance Analysis of Tucana III, the Second $r$-process Enhanced Ultra-Faint Dwarf Galaxy
• An old, metal-poor globular cluster in Sextans A and the metallicity floor of globular cluster systems
• Chemical Abundance Analysis of Three $\alpha$-Poor, Metal-Poor Stars in the Ultra-Faint Dwarf Galaxy Horologium I
• Detailed Abundance Analysis of the Brightest Star in Segue 2, the Least Massive Galaxy
• The minimum metallicity of globular clusters and its physical origin -- implications for the galaxy mass-metallicity relation and observations of proto-globular clusters at high redshift
• A chemical confirmation of the faint Bootes II dwarf Spheroidal Galaxy
• Fe I oscillator strengths for transitions from high-lying odd-parity levels
• An inefficient dwarf: Chemical abundances and the evolution of the Ursa Minor dwarf spheroidal galaxy
• The chemical composition of a regular halo globular cluster: NGC 5897
• Detailed Abundances of 15 Stars in the Metal-Poor Globular Cluster NGC 4833
• Search for Extra-Tidal RR Lyrae Stars in Milky Way Globular Clusters From Gaia DR2
• Insights into the chemical composition of the metal-poor Milky Way halo globular cluster NGC 6426
• The Gaia-ESO Survey: Detailed Abundances in the Metal-poor Globular Cluster NGC 4372
• Chemical Abundances in NGC 5053: A Very Metal-Poor and Dynamically Complex Globular Cluster
• Chemical evolution of the metal poor Globular Cluster NGC 6809
• A Detailed Study of Giants and Horizontal Branch Stars in M68: Atmospheric Parameters and Chemical Abundances

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• Four-hundred Very Metal-Poor Stars Studied with LAMOST and Subaru. II. Elemental abundances
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