On disks and jet(s) in the defunct quasar M 87

Abstract

M 87 is a prime candidate of an old quasar where the fuelling rate has been reduced drastically to ≅ 10⁻³ Ṁ _Ed. Under this condition, accretion towards a rapidly rotating black hole occurs in an optically thin fashion. The accretion rate is limited to 10⁻³ Ṁ _Ed by the jet luminosity. This low-accretion rate is in agreement with the fuelling provided by stellar winds in the central core of M 87. Due to the low angular momentum of the stellar component in this giant elliptical, stellar mass-loss accumulates in a ring-like structure on the parsec-scale which is observed by HST. Accretion towards the central black hole occurs from here over geometrically thin advection dominated flows (ADAFs) that also drag inwards magnetic flux from the parsec-scale.

This magnetic structure builds up a dipolar magnetosphere which immerses the central black hole. Disk plasma is injected into rotating field lines that connect to the horizon. We discuss the energetics and wind properties of the magnetically driven outflows. The observed kinetic luminosity is essentially Poynting-flux transformed into kinetic energy along collimated flux-tubes. The injection conditions near the horizon determine the asymptotic outflow velocities, Lorentz factors of 3 – 5 are quite natural. The resulting collimation radius is in agreement with VLBI data.