ar X iv : a st ro - p h / 06 12 17 5 v 1 7 D ec 2 00 6 Global MHD instabilities : from Low Frequency to High Frequency QPOs , and to Sgr A *

ar X iv : a st ro - p h / 06 12 53 0 v 1 1 9 D ec 2 00 6 High sensitivity low frequency radio observations of cD galaxies

We present the GMRT 235 MHz images of three radio galaxies and 610 MHz images of two sources belonging to a complete sample of cD galaxies in rich and poor galaxy clusters. The analysis of the spectral properties confirms the presence of aged radio emission in two of the presented sources.

ar X iv : a st ro - p h / 06 12 59 5 v 1 2 0 D ec 2 00 6 Tracing Ghost Cavities with Low Frequency Radio Observations

We present X-ray and multi-frequency radio observations of the central radio sources in several X-ray cavity systems. We show that targeted radio observations are key to determining if the lobes are being actively fed by the central AGN. Low frequency observations provide a unique way to study both the lifecycle of the central radio source as well as its energy input into the ICM over several o...

ar X iv : a st ro - p h / 06 12 37 8 v 1 1 4 D ec 2 00 6 Magnetic fields , strings and cosmology

ar X iv : a st ro - p h / 06 12 42 6 v 1 1 5 D ec 2 00 6 Heating and Cooling in the Perseus Cluster Core

ar X iv : a st ro - p h / 06 07 12 3 v 1 7 J ul 2 00 6 Accretion models of Sgr A *

The supermassive black hole in the center of our Galaxy, Sgr A*, is unique because the angular size of the black hole is the largest in the sky thus providing detailed boundary conditions on, and much less freedom for, accretion flow models. In this paper I review advection-dominated accretion flow (ADAF; another name is radiatively inefficient accretion flow) models for Sgr A*. This includes t...