The Populations of Carina. II. Chemical Enrichment

Date

2017

Authors

Norris, John
Yong, David
Venn, Kim
Gilmore, Gerard
Casagrande, Luca
Dotter, Aaron

Journal Title

Journal ISSN

Volume Title

Publisher

Institute of Physics Publishing

Abstract

Chemical abundances are presented for 19 elements in a sample of 63 red giants in the Carina dwarf spheroidal galaxy (dSph), based on homogeneous 1D/LTE model atmosphere analyses of our own observations (32 stars) and data available in the literature (a further 31 independent stars). The (Fe) metallicity and [α/Fe] distribution functions have mean values and dispersions of −1.59 and 0.33 dex ([Fe/H] range: −2.68 to −0.64) and 0.07 and 0.13 dex ([α/Fe] range: −0.27 to 0.25), respectively. We confirm the finding of Venn et al. that a small percentage (some 10% in the present investigation) of the sample shows clear evidence for significant enrichment by Type Ia supernova (SN Ia) ejecta. Calcium, with the most accurately determined abundance of the α-elements, shows an asymmetric distribution toward smaller values of [Ca/Fe] at all [Fe/H], most significantly over −2.0 < [Fe/H] < −1.0, suggestive of incomplete mixing of the ejecta of SNe Ia with the ambient medium of each of Carina's generations. Approximate color–magnitude diagram age estimates are presented for the sample, and together with our chemical abundances, compared with the results of our previous synthetic color–magnitude diagram analysis, which reported the details of Carina's four well-defined populations. We searched for the Na–O anticorrelation universally reported in the Galaxy's globular clusters and confirm that this phenomenon does not exist in Carina. We also found that one of the 32 stars in our sample has an extremely enhanced lithium abundance—A(Li)NLTE = +3.36, consistent with membership of the ~1% group of Li-rich stars in dSph described by Kirby et al.

Description

Keywords

Citation

Source

Astrophysical Journal Supplement Series

Type

Journal article

Book Title

Entity type

Access Statement

License Rights

DOI

10.3847/1538-4365/aa755e

Restricted until