How do atomic code uncertainties affect abundance measurements in the intracluster medium?

TL;DR

This study compares atomic spectral models to assess uncertainties in measuring chemical abundances in the intracluster medium, revealing significant discrepancies that depend on the atomic code and instrument used.

Contribution

It provides a comprehensive comparison between two major atomic codes, highlighting their differences and the impact on abundance measurements in the ICM.

Findings

Differences up to 20% in Fe abundance between codes.

Discrepancies up to 45% in element ratios like O/Fe, Mg/Fe.

Discrepancies are instrument-dependent, affecting absolute Fe measurements.

Abstract

Accurate chemical abundance measurements of X-ray emitting atmospheres pervading massive galaxies, galaxy groups, and clusters provide essential information on the star formation and chemical enrichment histories of these large scale structures. Although the collisionally ionised nature of the intracluster medium (ICM) makes these abundance measurements relatively easy to derive, underlying spectral models can rely on different atomic codes, which brings additional uncertainties on the inferred abundances. Here, we provide a simple, yet comprehensive comparison between the codes SPEXACT v3.0.5 (cie model) and AtomDB v3.0.9 (vapec model) in the case of moderate, CCD-like resolution spectroscopy. We show that, in cool plasmas ($kT \lesssim 2$ keV), systematic differences up to $\sim$20% for the Fe abundance and $\sim$45% for the O/Fe, Mg/Fe, Si/Fe, and S/Fe ratios may still occur. Importantly, these discrepancies are also found to be instrument-dependent, at least for the absolute Fe abundance. Future improvements in these two codes will be necessary to better address questions on the ICM enrichment.