M84 - Can the AGN Affect The Orientation of The Disk?

Abstract

In M84 dust features are not aligned with the galaxy isophotes but are perpendicular to the radio jets. We estimate the timescale that the gas disk should precess in the galaxy. Since this timescale is short ($\sim 2\times 10^7$ years at 100 pc) we consider mechanisms that could cause the gas disk to be misaligned with the galaxy. One possibility is that a cooling flow replenishes the disk on this timescale and at angles that vary with radius. Another possibility is that there is a pressure on the disk that is large enough to overcome the torque from the galaxy. We estimate this pressure and find that it can be provided by ram pressure from an energetic interstellar medium that is consistent with velocity dispersions observed in ionized gas and densities estimated from the X-ray emission. We therefore propose that an AGN associated energetic interstellar medium is responsible for causing the gas disk in M84 to be misaligned with the galaxy isophotal major axis for $r \lta 600$ pc. We propose that AGN associated outflows or kinetic motion in low density media could be responsible for jet/disk alignments observed on 100 pc scales in nearby radio galaxies.