A very deep Chandra view of metals, sloshing and feedback in the Centaurus cluster of galaxies

Abstract: We examine deep Chandra X-ray observations of the Centaurus cluster of galaxies, Abell 3526. Applying a gradient magnitude filter reveals a wealth of structure, from filamentary soft emission on 100pc (0.5 arcsec) scales close to the nucleus to features 10s of kpc in size at larger radii. The cluster contains multiple high-metallicity regions with sharp edges. Relative to an azimuthal average, the deviations of metallicity and surface brightness are correlated, and the temperature is inversely correlated, as expected if the larger scale asymmetries in the cluster are dominated by sloshing motions. Around the western cold front are a series of ~7 kpc 'notches', suggestive of Kelvin-Helmholtz instabilities. The cold front width varies from 4 kpc down to close to the electron mean free path. Inside the front are multiple metallicity blobs on scales of 5-10 kpc, which could have been uplifted by AGN activity, also explaining the central metallicity drop and flat inner metallicity profile. Close to the nucleus are multiple shocks, including a 1.9-kpc-radius inner shell-like structure and a weak 1.1-1.4 Mach number shock around the central cavities. Within a 10 kpc radius are 9 depressions in surface brightness, several of which appear to be associated with radio emission. The shocks and cavities imply that the nucleus has been repeatedly active on 5-10 Myr timescales, indicating a tight balance between heating and cooling. We confirm the presence of a series of linear quasi-periodic structures. If they are sound waves, the ~5 kpc spacing implies a period of 6 Myr, similar to the ages of the shocks and cavities. Alternatively, these structures may be Kelvin-Helmholtz instabilities, their associated turbulence or amplified magnetic field layers.

An In-Depth Analysis of the Centaurus Cluster Using Chandra X-Ray Observations

The paper "A Very Deep Chandra View of Metals, Sloshing, and Feedback in the Centaurus Cluster of Galaxies" provides an extensive examination of the Centaurus cluster, Abell 3526, utilizing a series of deep X-ray observations from the Chandra X-ray Observatory. This study primarily focuses on elucidating the structures associated with metals, sloshing motions, and feedback mechanisms within the cluster.

The methods employed include advanced imaging techniques such as gradient filtering, allowing for the identification of intricate features in the cluster's X-ray emission. One of the most notable observations is the spatial correlation between metallicity and SB, as well as the inverse correlation with temperature—indicative of sloshing motions. The study provides evidence of high-metallicity regions with well-defined boundaries and associating these with sloshing as a dominant mechanism influencing the cluster's larger-scale asymmetries.

A particular highlight is the systematic investigation of the western cold front in the cluster. The paper presents robust evidence for Kelvin-Helmholtz instabilities with characteristic scales of approximately 7 kpc, depicted by 'notches' along the cold front edge. Furthermore, the front's width is found to be narrower than or comparable to the collisional electron mean free path in several sectors, providing constraints on the cluster's microphysical processes.

In the cluster's core, the authors identify a 1.9-kpc-radius shell-like structure, hypothesized as a shock wave from a recent AGN outburst within the last ~3.5 Myr. This shock, in conjunction with multiple X-ray cavities, suggests recurrent AGN activity on 5–10 Myr timescales. The study also confirms the presence of quasi-periodic SB variations, potentially sound waves, with a spacing consistent with these timelines.

The observed central metallicity drop is consistent with a model where metals are initially locked in dust grains, which are subsequently uplifted by AGN-driven processes. These findings imply efficient metal transport mechanisms in galaxy clusters, facilitated by AGN feedback.

From a thermal perspective, the cluster exhibits a complex multiphase structure with evidence of a broad range of gas temperatures down to 0.7 keV. The presence of X-ray-emitting filaments correlating with cooler dust lanes is highlighted as an intriguing aspect of the cluster's core dynamics.

This research advances the understanding of AGN feedback and the role of sloshing in the evolution of galaxy clusters. The detailed observation of instabilities, shock structures, and metallicity distribution offers substantial insights into the intricate interplay of processes within the intracluster medium. Future exploration with upcoming missions like Athena is anticipated to provide even deeper insights by facilitating high-precision spectral measurements and improving the understanding of the chemical enrichment and cooling processes in clusters like Centaurus.