High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the SkyMapper Survey

Abstract

The SkyMapper Southern Sky Survey is carrying out a search for the most metal-poor stars in the Galaxy. It identifies candidates by way of its unique filter set that allows for estimation of stellar atmospheric parameters. The set includes a narrow filter centered on the Ca II K 3933A line, enabling a robust estimate of stellar metallicity. Promising candidates are then confirmed with spectroscopy. We present the analysis of Magellan-MIKE high-resolution spectroscopy of 122 metal-poor stars found by SkyMapper in the first two years of commissioning observations. 41 stars have [Fe/H] <= -3.0. Nine have [Fe/H] <= -3.5, with three at [Fe/H] ~ -4. A 1D LTE abundance analysis of the elements Li, C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, Ba and Eu shows these stars have [X/Fe] ratios typical of other halo stars. One star with low [X/Fe] values appears to be "Fe-enhanced," while another star has an extremely large [Sr/Ba] ratio: >2. Only one other star is known to have a comparable value. Seven stars are "CEMP-no" stars ([C/Fe] > 0.7, [Ba/Fe] < 0). 21 stars exhibit mild r-process element enhancements (0.3 <=[Eu/Fe] < 1.0), while four stars have [Eu/Fe] >= 1.0. These results demonstrate the ability to identify extremely metal-poor stars from SkyMapper photometry, pointing to increased sample sizes and a better characterization of the metal-poor tail of the halo metallicity distribution function in the future.

Minor corrections to text, missing data added to Tables 3 and 4; updated to match published version. Complete tables included in source

References in corpus (29)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Galactic chemical evolution: Carbon through Zinc
• Nucleosynthetic signatures of the first stars
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• An extremely primitive halo star
• Carbon-Enhanced Metal-Poor Star Frequencies in the Galaxy: Corrections for the Effect of Evolutionary Status on Carbon Abundances
• The Mass Spectrum of the First Stars
• HE 0557-4840 - Ultra-Metal-Poor and Carbon-Rich
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• Neutron-capture elements in the very metal-poor star HD122563
• Segue 1: An Unevolved Fossil Galaxy from the Early Universe
• NLTE abundances of Mn in a sample of metal-poor stars
• A non-LTE study of neutral and singly-ionized calcium in late-type stars
• The s process in massive stars at low metallicity. Effect of primary N14 from fast rotating stars
• The stellar content of the Hamburg/ESO survey. IV. Selection of candidate metal-poor stars
• Bright Metal-Poor Stars from the Hamburg/ESO Survey. I. Selection and Follow-up Observations from 329 Fields
• Stellar Archaeology -- Exploring the Universe with Metal-Poor Stars
• Carbon-Enhanced Metal-Poor Stars. III. Main-Sequence Turn-Off Stars from the SDSS/SEGUE Sample
• The Best and Brightest Metal-Poor Stars
• Evolution of the Barium abundance in the early Galaxy from a NLTE analysis of the Ba lines in a homogeneous sample of EMP stars
• Exploring the Origin of Lithium, Carbon, Strontium and Barium with four new Ultra Metal-Poor Stars
• How many nucleosynthesis processes exist at low metallicity?
• Spectroscopic analysis of metal-poor stars from LAMOST: early results
• Nine New Metal-Poor Stars on the Subgiant and Red Horizontal Branches with High Levels of r-process Enhancement
• The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge
• The origin of low [alpha/Fe] ratios in extremely metal-poor stars
• NGC 6522: A typical globular cluster in the Galactic bulge without signatures of rapidly rotating Population III stars

Cited by in corpus (55)

• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• Complete element abundances of nine stars in the r-process galaxy Reticulum II
• Four-hundred Very Metal-Poor Stars Studied with LAMOST and Subaru. II. Elemental abundances
• 3D NLTE analysis of the most iron-deficient star, SMSS0313-6708
• The lowest detected stellar Fe abundance: The halo star SMSS J160540.18-144323.1
• Magnetorotational supernovae: A nucleosynthetic analysis of sophisticated 3D models
• Evidence for an aspherical Population III supernova explosion inferred from the hyper metal-poor star HE1327-2326
• Predicting the locations of possible long-lived low-mass first stars: Importance of satellite dwarf galaxies
• Constraining cosmic scatter in the Galactic halo through a differential analysis of metal-poor stars
• The R-Process Alliance: Chemo-Dynamically Tagged Groups of Halo $r$-Process-Enhanced Stars Reveal a Shared Chemical-Evolution History
• Exploring the Galaxy's halo and very metal-weak thick disk with SkyMapper and Gaia DR2
• The Atari Disk, a Metal-Poor Stellar Population in the Disk System of the Milky Way
• The value-added catalogue for LAMOST DR8 low-resolution spectra
• Chemical abundances of damped Lyman alpha systems in the XQ-100 survey
• High-resolution spectroscopy of extremely metal-poor stars from SDSS/SEGUE. III. Unevolved Stars with $[Fe/H]\lesssim -3.5$
• High resolution spectroscopic follow-up of the most metal-poor candidates from SkyMapper DR1.1
• Stellar metallicities from SkyMapper photometry I: A study of the Tucana II ultra-faint dwarf galaxy
• The R-Process Alliance: The Peculiar Chemical Abundance Pattern of RAVE J183013.5-455510
• Constraints on stellar rotation from the evolution of Sr and Ba in the Galactic halo
• The chemical abundance pattern of the extremely metal-poor thin disk star 2MASS J1808-5104 and its origins
• The R-Process Alliance: J1521-3538, a very metal-poor, extremely r-process-enhanced star with [Eu/Fe]=+2.2, and the class of r-III stars
• Four-hundred Very Metal-poor Stars studied with LAMOST and Subaru. I. Survey Design, Follow-up Program, and Binary Frequency
• The R-Process Alliance: Chemo-Dynamically Tagged Groups II. An Extended Sample of Halo $r$-Process-Enhanced Stars
• Unusual neutron-capture nucleosynthesis in a carbon-rich Galactic bulge star
• The Origin of the Heaviest Metals in Most Ultra-Faint Dwarf Galaxies
• The Pristine survey -- XV. A CFHT ESPaDOnS view on the Milky Way halo and disc populations
• Decoding the compositions of four bright $r$-process-enhanced stars
• Extending the Chemical Reach of the H3 Survey: Detailed Abundances of the Dwarf-galaxy Stellar Stream Wukong/LMS-1
• Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental abundances
• Inferring the velocity of early massive stars from the abundances of extremely metal-poor stars
• Keck HIRES Spectroscopy of SkyMapper Commissioning Survey Candidate Extremely Metal-Poor Stars
• Search for Extremely Metal-Poor Stars with GEMINI-N/GRACES I. Chemical-Abundance Analysis
• Discovery of an $[Fe/H]\sim -4.8$ Star in $Gaia$ XP Spectra
• Finding $r$-II sibling stars in the Milky Way with the Greedy Optimistic Clustering algorithm
• GalCEM I -- An Open-Source Detailed Isotopic Chemical Evolution Code
• The Chemical Composition of Extreme-Velocity Stars
• Four Metal-poor Stars in the Sagittarius Dwarf Spheroidal Galaxy
• Untangling the Sources of Abundance Dispersion in Low-Metallicity Stars
• The SkyMapper search for extremely metal-poor stars in the Large Magellanic Cloud
• Europium enrichment and hierarchical formation of the Galactic halo
• Chemical Abundances of the Typhon Stellar Stream
• Abundance Analysis of New $r$-Process-Enhanced Stars from the HESP-GOMPA Survey
• Discovery of an Extremely r-process-enhanced Thin-disk Star with [Eu/H] = +0.78
• The oldest stars with low neutron-capture element abundances and origins in ancient dwarf galaxies
• The true nature of HE0057-5959, the most metal-poor Li-rich star
• Fuzzy Cluster Analysis: Application to Determining Metallicities for Very Metal-poor Stars
• M3DIS -- A grid of 3D radiation-hydrodynamics stellar atmosphere models for stellar surveys. II. Carbon-enhanced metal-poor stars
• The metal-poorest tail of the Galactic halo: hypothesis on its origin from precise spectral analysis
• Impact of the latest 22Ne+α reaction rates on nucleosynthesis in massive stars and galactic chemical evolution
• Proton-rich production of lanthanides: the $\nu i$ process
• Detailed Abundance Determination of Metal-Poor Stars with X-Shooter I. Unusual Chemistry in Halo Stars
• The R-Process Alliance: A Nearly Complete R-Process Abundance Template Derived from Ultraviolet Spectroscopy of the R-Process-Enhanced Metal-Poor Star HD 222925
• On the Chemical Composition of the Evolved Very Bright Metal-Poor Star HD 1936
• Silicon and Strontium abundances of very metal-poor stars determined from near-infrared spectra
• The GALAH Survey: A New Sample of Extremely Metal-Poor Stars Using A Machine Learning Classification Algorithm