The virgo cluster — home of M 87

Abstract

Our current understanding of the structure and dynamics of the Virgo cluster is reviewed. Special emphasis is given to a possible connection between the activity of M 87 and the cluster as a whole. The Virgo cluster is an aggregate of at least three separate subclusters, centered on M 87, M 86, and M 49. The dominant M 87 subclump, with a mass of a few 10¹⁴ M_⊙, is outweighing the other two subclumps by an order of magnitude. There is evidence, from the kinematics of dwarf galaxies and the structure of the X-ray gas, that the M 86 subclump is falling into the M 87 subclump from the back with a relative velocity of ≈ 1 500 km s⁻¹. M 87 and M 86 seem to be embedded in a common, cocoon-like swarm of dwarf ellipticals. The orientation of this cocoon, or simply the line connecting M 87 and M 86, is coinciding with the (projected) direction of the jet of M 87. A possible explanation for this apparent coherence between structures on the pc scale of the center of M 87 and the Mpc scale of the Virgo cluster is discussed.