Elemental Abundances in the X-Ray Gas of Early-Type Galaxies with XMM and Chandra Observations

TL;DR

This study measures the elemental abundances in the hot gas of early-type galaxies using XMM-Newton and Chandra data, finding lower-than-expected supernova enrichment levels, challenging existing models of galaxy gas composition.

Contribution

It provides detailed measurements of gas-phase elemental abundances in early-type galaxies, testing predictions of supernova enrichment and stellar mass loss contributions.

Findings

Median Fe and O abundances are below Solar values.

Abundances are consistent across different instruments and aperture sizes.

Supernova enrichment in the gas is less than expected.

Abstract

The source of hot gas in elliptical galaxies is thought to be due to stellar mass loss, with contributions from supernova events and possibly from infall from a surrounding environment. This picture predicts supersolar values for the metallicity of the gas toward the inner part of the galaxy, which can be tested by measuring the gas phase abundances. We use high-quality data for 10 nearby early-type galaxy from XMM-Newton, featuring both the EPIC and the Reflection Grating Spectrometer, where the strongest emission lines are detected with little blending; some Chandra data are also used. We find excellent consistency in the elemental abundances between the different XMM instruments and good consistency with Chandra. Differences in abundances with aperture size and model complexity are examined, but large differences rarely occur. For a two-temperature thermal model plus a point source contribution, the median Fe and O abundances are 0.86 and 0.44 of the Solar value, while Si and Mg abundances are similar to that for Fe. This is similar to stellar abundances for these galaxies but supernovae were expected to enhance the gas phase abundances considerably, which is not observed.