Searching for the missing iron mass in the core of the centaurus cluster

Abstract

We re-analyse a combined 198 ks Chandra observation of NGC 4696, 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 to ̃0.4 Z⊙, within the central 5 kpc of the cluster. We estimate that this central abundance drop corresponds to a total 'missing' iron mass of 1.4 × 106 M⊙. We propose that part of this missing iron is locked up in cool (̃ 19 K), far-infrared 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. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.