The Astrophysical Journal (Jan 2023)

Chemical Analysis of the Brightest Star of the Cetus II Ultrafaint Dwarf Galaxy Candidate

  • K. B. Webber,
  • T. T. Hansen,
  • J. L. Marshall,
  • J. D. Simon,
  • A. B. Pace,
  • B. Mutlu-Pakdil,
  • A. Drlica-Wagner,
  • C. E. Martínez-Vázquez,
  • M. Aguena,
  • S. S. Allam,
  • O. Alves,
  • E. Bertin,
  • D. Brooks,
  • A. Carnero Rosell,
  • J. Carretero,
  • L. N. da Costa,
  • J. De Vicente,
  • P. Doel,
  • I. Ferrero,
  • D. Friedel,
  • J. Frieman,
  • J. García-Bellido,
  • G. Giannini,
  • D. Gruen,
  • R. A. Gruendl,
  • S. R. Hinton,
  • D. L. Hollowood,
  • K. Honscheid,
  • K. Kuehn,
  • J. Mena-Fernández,
  • F. Menanteau,
  • R. Miquel,
  • R. L. C. Ogando,
  • M. E. S. Pereira,
  • A. Pieres,
  • A. A. Plazas Malagón,
  • E. Sanchez,
  • B. Santiago,
  • J. Allyn Smith,
  • M. Smith,
  • E. Suchyta,
  • G. Tarle,
  • C. To,
  • N. Weaverdyck,
  • B. Yanny

DOI
https://doi.org/10.3847/1538-4357/ad0385
Journal volume & issue
Vol. 959, no. 2
p. 141

Abstract

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We present a detailed chemical abundance analysis of the brightest star in the ultrafaint dwarf (UFD) galaxy candidate Cetus II from high-resolution Magellan/MIKE spectra. For this star, DES J011740.53-173053, abundances or upper limits of 18 elements from carbon to europium are derived. Its chemical abundances generally follow those of other UFD galaxy stars, with a slight enhancement of the α -elements (Mg, Si, and Ca) and low neutron-capture element (Sr, Ba, and Eu) abundances supporting the classification of Cetus II as a likely UFD. The star exhibits lower Sc, Ti, and V abundances than Milky Way (MW) halo stars with similar metallicity. This signature is consistent with yields from a supernova originating from a star with a mass of ∼11.2 M _⊙ . In addition, the star has a potassium abundance of [K/Fe] = 0.81, which is somewhat higher than the K abundances of MW halo stars with similar metallicity, a signature that is also present in a number of UFD galaxies. A comparison including globular clusters and stellar stream stars suggests that high K is a specific characteristic of some UFD galaxy stars and can thus be used to help classify objects as UFD galaxies.

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