Searching for the missing iron in the core of the Centaurus cluster

TL;DR

This study re-analyzes Chandra data of the Centaurus cluster's core, revealing a sharp drop in iron abundance likely due to iron being locked in dust grains within cold gas filaments, influenced by feedback processes.

Contribution

It identifies a significant iron abundance drop in the cluster core and proposes a novel explanation involving iron sequestration in dust grains within cold gas filaments.

Findings

Iron abundance drops from ~1.8 to ~0.4 Zsolar within 5 kpc.

Estimated missing iron mass is 1.4 million solar masses.

Iron may be locked in dust grains within cold gas filaments.

Abstract

We re-analyse a combined 198 ks Chandra observation of NGC4696, the brightest galaxy of the Centaurus cluster. We extract temperature and metallicity profiles from the data, and we confirm the presence of a sharp drop in iron abundance, from ~1.8 Zsolar to ~0.4 Zsolar, within the central 5 kpc of the cluster. We estimate that this abundance drop corresponds to a total "missing" iron mass of 1.4e06 Msolar. We propose that part of this missing iron is locked up in cool (~19 K) far-IR emitting dust, as found by Spitzer and Herschel observations. This can occur if the iron injected by stellar mass loss in the central region is in grains, which remain in that form as the injected dusty cold gas mixes and joins the cold dusty filamentary nebula observed within the same region. The bubbling feedback process observed in the cluster core then drags filaments outward and dumps them at 10-20 kpc radius, where the metallicity is high.