A VLBA Study of Core Wander and Relative Proper Motion of M87 and M84

Fredrick Davies (NMT/NRAO), Craig Walker (NRAO), Joan Wrobel (NRAO), Chun Ly (UCLA), William Junor (LANL), Philip Hardee (U. Alabama)

M87, the dominant galaxy in the Virgo Cluster, has a supermassive black hole of 3x10^9 solar masses that emits a jet detectable from radio to X-ray wavelengths. Between January 2007 and April 2008, M87 was observed 34 times with the VLBA to study the dynamics in the jet's launch and collimation regions. Throughout that study, the relative positions of M87 and M84, another Virgo elliptical about 1.5 degrees away, were measured using phase-referencing. These relative positions have also been compared with one determined from archival 2001 data in an attempt to measure proper motion of M84.