Intrinsic Structure and Kinematics of the Sub-Parsec Scale Jet of M87

TL;DR

This study uses VLBA observations at 15 GHz to analyze the sub-parsec jet structure of M87, revealing limb brightening, low apparent speeds, and a spine-sheath velocity gradient consistent with TeV emission models.

Contribution

It provides new high-resolution imaging evidence of the jet's limb brightening and velocity structure, supporting the spine-sheath model in M87's jet.

Findings

Detected limb brightened jet and counter-feature.

Measured jet speeds less than 0.05c.

Observed jet to counter-jet flux ratio > 200.

Abstract

We report new results from a sub-parsec scale study of the inner jet in M87 performed at 15 GHz with the Very Long Baseline Array. We have detected a limb brightened structure of the jet along with a faint 3 mas long counter-feature which we also find to be limb brightened. Typical speeds of separate jet features are measured to be less than 0.05 speed of light, despite the highly asymmetric jet structure and the implications of the canonical relativistic beaming scenario. The observed intrinsic jet structure can be described in terms of a two stream spine-sheath velocity gradient across the jet according to theoretical predications based on the recently discovered strong and variable TeV emission from M87. The jet to counter-jet flux density ratio is measured to be greater than 200. The observed intrinsic jet structure is broadly consistent with theoretical predictions of a spine-sheath velocity gradient suggested by recently discovered TeV emission from M87.