The iron abundance of the Magellanic Bridge

TL;DR

This study measures iron abundances in stars of the Magellanic Bridge and Clouds, revealing significantly lower metallicities than in the Milky Way, suggesting metal-poor material was stripped from the SMC.

Contribution

First detailed UV spectral analysis of iron abundances in Magellanic Bridge stars, highlighting systematic differences and implications for galaxy interactions.

Findings

Bridge stars have iron abundances about -0.5 dex lower than SMC and LMC.

Bridge stars show similar low abundances in C, N, O, Mg, Si, around -1.1 dex.

Systematic errors may affect absolute abundances but not differential results.

Abstract

High-resolution HST ultra-violet spectra for five B-type stars in the Magellanic Bridge and in the Large and Small Magellanic Clouds have been analysed to estimate their iron abundances. Those for the Clouds are lower than estimates obtained from late-type stars or the optical lines in B-type stars by approximately 0.5 dex. This may be due to systematic errors possibly arising from non-LTE effects or from errors in the atomic data as similar low Fe abundances having previously been reported from the analysis of the ultra-violet spectra of Galactic early-type stars. The iron abundance estimates for all three Bridge targets appear to be significantly lower than those found for the SMC and LMC by approximately -0.5 dex and -0.8 dex respectively and these differential results should not be affected by any systematic errors present in the absolute abundance estimates. These differential iron abundance estimates are consistent with the underabundances for C, N, O, Mg and Si of approximately -1.1 dex relative to our Galaxy previously found in our Bridge targets. The implications of these very low metal abundances for the Magellanic Bridge are discussed in terms of metal deficient material being stripped from the SMC.