• DOI:10.3847/1538-4357/ab9643
• Corpus ID: 218763518

Chemical Analysis of the Ultrafaint Dwarf Galaxy Grus II. Signature of High-mass Stellar Nucleosynthesis

@article{Hansen2020ChemicalAO,
  title={Chemical Analysis of the Ultrafaint Dwarf Galaxy Grus II. Signature of High-mass Stellar Nucleosynthesis},
  author={Terese T. Hansen and Jennifer L. Marshall and Joshua D. Simon and T. S. Li and R. A. Bernstein and Andrew B. Pace and P. S. Ferguson and Daniel Q. Nagasawa and Kyler W. Kuehn and Daniela Carollo and Marla C. Geha and David J. James and Alistair R. Walker and H. Thomas Diehl and Michel Aguena and Sahar Allam and Santiago {\'A}vila and Emmanuel Bertin and David Brooks and Elizabeth Buckley-Geer and David L. Burke and Aurelio Carnero Rosell and Matias Carrasco Kind and Jorge Carretero and Matteo Costanzi and L. N. da Costa and Shantanu Desai and Juan de Vicente and Peter Doel and Kathleen D. Eckert and T. F. Eifler and S. Everett and I. Ferrero and Joshua A. Frieman and Juan Garc{\'i}a-Bellido and Enrique Gazta{\~n}aga and David W. Gerdes and Daniel Gruen and Robert A. Gruendl and Julia Gschwend and Gaston R. Guti{\'e}rrez and Samuel R. Hinton and Devon L. Hollowood and Klaus Honscheid and Nikolay Kuropatkin and Marcio A. G. Maia and M March and Ramon Miquel and Antonella Palmese and Francisco Paz-Chinch{\'o}n and Andreas Alejandro Plazas and Eusebio S{\'a}nchez and Bas{\'i}lio Xavier Santiago and Victor E. Scarpine and Santiago Serrano and M. Smith and Marcelle Soares-Santos and Eric Suchyta and Mollye E. C. Swanson and Gregory G. Tarl{\'e} and T. N. Varga and R. D. Wilkinson},
  journal={The Astrophysical Journal},
  year={2020},
  volume={897}
}

• T. Hansen, J. Marshall, +59 authors R. Wilkinson
• Published 21 May 2020
• Physics
• The Astrophysical Journal

We present a detailed abundance analysis of the three brightest member stars at the top of the giant branch of the ultrafaint dwarf (UFD) galaxy Grus II. All stars exhibit a higher than expected [Mg/Ca] ratio compared to metal-poor stars in other UFD galaxies and in the Milky Way (MW) halo. Nucleosynthesis in high-mass ( 20 M⊙) core-collapse supernovae has been shown to create this signature. The abundances of this small sample (three) stars suggests the chemical enrichment of Grus II could have occurred through substantial high-mass stellar evolution, and is consistent with the framework of a top-heavy initial mass function. However, with only three stars it cannot be ruled out that the abundance pattern is the result of a stochastic chemical enrichment at early times in the galaxy. The most metal-rich of the three stars also possesses a small enhancement in rapid neutron-capture (r-process) elements. The abundance pattern of the r-process elements in this star matches the scaled r-process pattern of the solar system and r-process enhanced stars in other dwarf galaxies and in the MW halo, hinting at a common origin for these elements across a range of environments. All current proposed astrophysical sites of r-process element production are associated with high-mass stars, thus the possible top-heavy initial mass function of Grus II would increase the likelihood of any of these events occurring. The time delay between the α and r-process element enrichment of the galaxy favors a neutron star merger as the origin of the r-process elements in Grus II.