Brigthest Cluster Galaxies Unique class of objects  most luminous  most massive  extended source  some BCG shows multiple nuclei → galaxy merger → cD galaxy - only in clusters - L vs cluster properties also giant E and D galaxy  Close to the peak of the cluster X-Ray emission  strong offset from FP but little scatter  different formation history They are more likely to host radio-loud AGN than other galaxies of the same mass BCG in Radio Band (Best et al. 2006) Statistical study of parsec scale properties of a complete sample of BCGs is fundamental. Abell Clusters with DC ≤ 2 and Declination > 0 deg. Outside the Sample.... (to increase the statistic ) Abell Clusters but with DC>2 Our project

EXTENDEDSAMPLEEXTENDEDSAMPLE NB: WAT in non cool core clusters (Owen et al. 1985) NB: Core+halo in cool core clusters (Burns 1990) - 5 GHz VLBA observations  new for 23/27 sources

Cluster morphology # two-sided one-sided point N.D. BCG in relaxed clusters: 10 7 (70%) - 1 (10%) 2 (20%)‏ BCG in merging clusters: (59%) 1 (5%) 8 (36%)‏ From our complete sample (nearby clusters) and literature data Not detected sources are mostly BCGs with a radio quiet core also in VLA images (Liuzzo et al. 2010) Strong dichotomy Comparison sample: Bologna Complete Sample: no selection effect on jet velocity and orientation 27% of FR I radio galaxies (same radio power range of BCG) have a two-sided jet  random angle distribution of sources with relativistic (Liuzzo et al. 2009).  FR I not BCG and BCG in merging clusters similar pc scale properties  relativistic effects in intrinsically symmetric jets.  BCG in cooling clusters different pc scale properties  mildly relativistic jets  interaction with the surrounding medium ? Why/how mildly relativistic pc-scale jets in cooling clusters? Rossi et al model  Ratio between ISM and jet density is important for pc scale jet deceleration CO emission  Dense ISM 15 GHz VLBA 86 GHz VLBA 3C 84