Not-so-heavy metal(s): Chemical Abundances in the Ultra-faint Dwarf Galaxies Eridanus IV and Centaurus I

TL;DR

This study provides detailed chemical abundance measurements of the brightest stars in two ultra-faint dwarf galaxies, revealing their extremely low metallicities, carbon enhancement, and neutron-capture deficiencies, which inform galaxy formation and chemical evolution models.

Contribution

First detailed high-resolution chemical abundance analysis of stars in Eridanus IV and Centaurus I ultra-faint dwarf galaxies, highlighting their unique chemical signatures.

Findings

EriIV-9808 is extremely metal-poor and carbon-enhanced.

CenI-5136 has metallicity [Fe/H] = -2.52 and typical ultra-faint dwarf galaxy chemistry.

Both stars are neutron-capture deficient, consistent with ultra-faint dwarf galaxy stars.

Abstract

We present detailed chemical abundances of the brightest star in each of the ultra-faint dwarf galaxies Eridanus IV and Centaurus I using high-resolution Magellan/MIKE spectroscopy. The brightest star in Centaurus I, CenI-5136, is a very metal-poor star with metallicity [Fe/H] = $-2.52\pm0.17$ and chemical abundances typical of a star in an ultra-faint dwarf galaxy. We confirm that the star in Eridanus IV, EriIV-9808, is extremely metal-poor ([Fe/H] = $-3.25\pm0.19$) and find that it is carbon-enhanced, with [C/Fe] = $1.07\pm0.34$, as is common for many stars at this metallicity. Both stars are also neutron-capture deficient, which is typical of stars in ultra-faint dwarf galaxies, but less common in other environments. We consider possible enrichment scenarios for EriIV-9808 and tentatively conclude that it is unlikely to be the descendant of a single Pop III progenitor, despite its carbon-enhancement and low metallicity.