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

abstract

  • Abstract 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 GrusII. 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 GrusII 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 GrusII would increase the likelihood of any of these events occurring. The time delay between the and r-process element enrichment of the galaxy favors a neutron star merger as the origin of the r-process elements in GrusII.

published proceedings

  • ASTROPHYSICAL JOURNAL

altmetric score

  • 10.58

author list (cited authors)

  • Hansen, T. T., Marshall, J. L., Simon, J. D., Li, T. S., Bernstein, R. A., Pace, A. B., ... Wilkinson, R.

citation count

  • 22

complete list of authors

  • Hansen, TT||Marshall, JL||Simon, JD||Li, TS||Bernstein, RA||Pace, AB||Ferguson, P||Nagasawa, DQ||Kuehn, K||Carollo, D||Geha, M||James, D||Walker, A||Diehl, HT||Aguena, M||Allam, S||Avila, S||Bertin, E||Brooks, D||Buckley-Geer, E||Burke, DL||Carnero Rosell, A||Carrasco Kind, M||Carretero, J||Costanzi, M||Da Costa, LN||Desai, S||De Vicente, J||Doel, P||Eckert, K||Eifler, TF||Everett, S||Ferrero, I||Frieman, J||Garcia-Bellido, J||Gaztanaga, E||Gerdes, DW||Gruen, D||Gruendl, RA||Gschwend, J||Gutierrez, G||Hinton, SR||Hollowood, DL||Honscheid, K||Kuropatkin, N||Maia, MAG||March, M||Miquel, R||Palmese, A||Paz-Chinchon, F||Plazas, AA||Sanchez, E||Santiago, B||Scarpine, V||Serrano, S||Smith, M||Soares-Santos, M||Suchyta, E||Swanson, MEC||Tarle, G||Varga, TN||Wilkinson, R

publication date

  • July 2020