Radio AGN in 13,240 galaxy clusters from the Sloan Digital Sky Survey

We correlate the positions of 13,240 Brightest Cluster Galaxies (BCGs) with 0.1 <= z <= 0.3 from the maxBCG catalog with radio sources from the FIRST survey to study the sizes and distributions of radio AGN in galaxy clusters. We find that 19.7% of our BCGs are associated with FIRST sources, and this fraction depends on the stellar mass of the BCG, and to a lesser extent on the richness of the parent cluster (in the sense of increasing radio loudness with increasing mass). The intrinsic size of the radio emission associated with the BCGs peaks at 55 kpc, with a tail extending to 200 kpc. The radio power of the extended sources places them on the divide between FR I and FR II type sources, while sources compact in the radio tend to be somewhat less radio-luminous. We also detect an excess of radio sources associated with the cluster, instead of with the BCG itself, extending out to ~1.4 Mpc.Comment: 14 pages, 6 figures, accepted for publication in ApJ

Finite element microstructural homogenization techniques and intergranular, intragranular microstructural effects on effective diffusion coefficient of heterogeneous polycrystalline composite media

Microstructural intergranular and intragranular effects play a vitally important role in mass transport within heterogeneous polycrystalline composite media. Full scale macroscopic specimen or component modelling of heterogeneous polycrystalline composite media is complex, time consuming and computationally expensive. Consequently it is important to develop a homogenous model to predict the effective diffusion coefficient of the heterogeneous polycrystalline composite media. It is also important to investigate the effect of intergranular and intragranular microstructure on effective diffusivity of heterogeneous polycrystalline composite media. A two dimensional finite element microstructural representative volume element (FEMRVE) model with different intergranular and intragranular microstructures has been developed using the well-known Voronoi tessellation technique. The effective diffusivity predicted by the FEMRVE model with various intergranular and intragranular microstructures of heterogeneous polycrystalline composite media agrees well with the results of various effective medium theories