A volume-limited sample of X-ray galaxy groups and clusters: III. Central abundance drops

TL;DR

This study investigates central abundance drops in a volume-limited sample of 101 X-ray galaxy groups and clusters, revealing their association with X-ray cavities and cooling times, and highlighting the importance of data quality for detection.

Contribution

It provides the first systematic analysis of central abundance drops in a volume-limited sample, linking these drops to X-ray cavities and dust processes, and clarifies detection conditions.

Findings

8 of 65 sources have certain central abundance drops

All sources with drops have X-ray cavities

Detection depends on counts >13000 in central 20 kpc

Abstract

We present the results of a search and study of central abundance drops in a volume-limited sample (z<=0.071) of 101 X-ray galaxy groups and clusters. These are best observed in nearby, and so best resolved, groups and clusters, making our sample ideal for their detection. Out of the 65 groups and clusters in our sample for which we have abundance profiles, 8 of them have certain central abundance drops, with possible central abundance drops in another 6. All sources with central abundance drops have X-ray cavities, and all bar one exception have a central cooling time <=1 Gyr. These central abundance drops can be generated if the iron injected by stellar mass loss processes in the core of these sources is in grains, which then become incorporated in the central dusty filaments. These, in turn, are dragged outwards by the bubbling feedback process in these sources. We find that data quality significantly affects the detection of central abundance drops, inasmuch as a higher number of counts in the central 20 kpc of a source makes it easier to detect a central abundance drop, as long as these counts are more than ~13000. On the other hand, the magnitude of the central abundance drop does not depend on the number of these counts, though the statistical significance of the measured drop does. Finally, in line with the scenario briefly outlined above, we find that, for most sources, the location of X-ray cavities acts as an upper limit to the location of the peak in the radial metallicity distribution.