paper

Chemical Analysis of the Ultra-Faint Dwarf Galaxy Grus~II. Signature of high-mass stellar nucleosynthesis

arXiv:2005.10767 · doi:10.3847/1538-4357/ab9643

Abstract

We present a detailed abundance analysis of the three brightest member stars at the top of the giant branch of the ultra-faint dwarf galaxy Grus~II. All stars exhibit a higher than expected ratio compared to metal-poor stars in other ultra-faint dwarf galaxies and in the Milky Way halo. Nucleosynthesis in high mass (M) core-collapse supernovae has been shown to create this signature. The abundances of this small sample (3) stars suggest 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 can not 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 (-process) elements. The abundance pattern of the -process elements in this star matches the scaled -process pattern of the solar system and -process enhanced stars in other dwarf galaxies and in the Milky Way halo, hinting at a common origin for these elements across a range of environments. All current proposed astrophysical sites of -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 and -process element enrichment of the galaxy favors a neutron star merger as the origin of the -process elements in Grus~II.

arXiv comment17 pages, 6 figures, accepted for publication in ApJ

References in corpus (61)

Cited by in corpus (18)