I/METAL BUDGET, SUPERNOVAE AND AGN FEEDBACK

BINGO! consortium

Work in progress

II/METAL IN EMISSION

BINGO! consortium

Work in progress

III/METAL IN  ABSORPTION

BINGO! consortium

Work in progress

IV/METAL TRANSPORT: THE ROLE OF AGN-DRIVEN CONVECTION

Rasera, Y., Lynch, B., Srivastava, K., Chandran, B., Abundance Profiles in Cooling-core Clusters: a Fossil Record of Past AGN-driven Convection?,  2008, ApJ, 689, 825

Abundance profile of galaxy clusters

Central peaks in the iron abundance of intracluster plasma are a common feature of cooling-core clusters.

Observations of the relative abundance of oxygen, silicon and iron suggest that the production of iron in these peaks is dominated by SNIa and winds from the central Brightest Cluster Galaxies (BCG).

Although centraly localized, these peaks have a much broader profile than the stars of the central Brightest Cluster Galaxies. If the amount of iron in these peaks is compatible with the amount produced within the BCG, the shape of these abundance profiles is still a mystery.  The distribution of iron is much broader than the stars that produce the metals. Which process transport iron from the BCG to the intracluster medium and increase the width of the profile? Is it related to the AGN feedback required to solve the cooling-flow problem?

Metal transport by AGN-driven convection

AGN-driven convection is a possible solution to the cooling-flow problem (see dark baryons). In this case, such turbulent motions should act as a diffusion process for the abundance profile. For our sample of eight clusters, we have therefore used the turbulent velocity profile that was deduced from the AGN-driven convection of Ben Chandran as well as the observed density and temperature profile of the clusters (see dark baryons). This serves as an input for an advection/diffusion model of the transport of metals in the intracluster medium. Assuming a constant turbulent level over a cluster’s lifetime, the turbulent velocities in the model can explain the observed abundance profile for five of the eight clusters.

Abundance profile as a record of past AGN-driven convection

However, AGN activity is certainly not constant over the cluster’s lifetime. We therefore reverse the problem and found which average AGN power in the past is required to explain the nowdays width of abundance profile. Interestingly, the required AGN power is compatible with typical AGN power values from observations. Abundance profile may therefore be a record of past AGN-driven convection. Of course, other sources may also contribute to the diffusion of the abundance profile.