The Edge of the M87 Halo and the Kinematics of the Diffuse Light in the Virgo Cluster Core ⋆

Abstract

Received 16.12.08; revised 25.03.09; accepted 22.04.09 Aims. To study the kinematics and dynamics of the extreme outer halo of M87, the central galaxy in the Virgo cluster, and its transition to the intracluster light (ICL). Methods. We present high resolution FLAMES/VLT spectroscopy of intracluster planetary nebula (PN) candidates, targeting three new fields in the Virgo cluster core with surface brightness down toµB = 28.5. Based on the projected phase space information (sky positions and line-of-sight velocities) we separate galaxy and cluster components in the confirmed PN sample. We then use the spherical Jeans equation and the total gravitational potential as traced by the X-ray emission to derive the orbital distribution in the outer stellar halo of M87. We determine the luminosity-specific PN number for the M87 halo and the ICL from the photometric PN catalogs and sampled luminosities, and discuss the origin of the ICL in Virgo based on its measured PN velocities. Results. We confirm a further 12 PNs in Virgo, five of which are bound to the halo of M87, and the remainder are true intracluster planetary nebulas (ICPNs). The M87 PNs are confined to the extended stellar envelope of M87, within a projected radius of ∼ 160