The Abundance Pattern in the Hot ISM of NGC 4472: Insights and Anomalies

TL;DR

This study analyzes the chemical composition of the hot interstellar medium in NGC 4472 using X-ray spectra, revealing abundance patterns that suggest a combination of stellar mass loss and supernova contributions, with some discrepancies from standard models.

Contribution

First detailed abundance pattern analysis of NGC 4472's hot ISM using Suzaku and XMM-Newton data, highlighting the role of supernovae and stellar processes in galaxy chemical evolution.

Findings

Abundance pattern includes O, Ne, Mg, Al, Si, S, Ar, Ca, Fe, Ni.

Present-day SNIa rate is 4-6 times lower than standard.

Standard nucleosynthesis models overproduce O relative to Ne and Mg.

Abstract

Important clues to the chemical and dynamical history of elliptical galaxies are encoded in the abundances of heavy elements in the X-ray emitting plasma. We derive the hot ISM abundance pattern in inner and outer regions of NGC 4472 from analysis of Suzaku spectra, supported by analysis of co-spatial XMM-Newton spectra. The low background and relatively sharp spectral resolution of the Suzaku XIS detectors, combined with the high luminosity and temperature in NGC 4472, enable us to derive a particularly extensive abundance pattern that encompasses O, Ne, Mg, Al, Si, S, Ar, Ca, Fe, and Ni in both regions. We apply simple chemical evolution models to these data, and conclude that the abundances are best explained by a combination of alpha-element enhanced stellar mass loss and direct injection of Type Ia supernova (SNIa) ejecta. We thus confirm the inference, based on optical data, that the stars in elliptical galaxies have supersolar alpha/Fe ratios, but find that that the present-day SNIa rate is 4-6 times lower than the standard value. We find SNIa yield sets that reproduce Ca and Ar, or Ni, but not all three simultaneously. The low abundance of O relative to Ne and Mg implies that standard core collapse nucleosynthesis models overproduce O by a factor of 2.