Observations of the Structure and Dynamics of the Inner M87 Jet

TL;DR

This study provides high-resolution, long-term observations of the M87 jet, revealing complex dynamics, acceleration, and structural features that enhance understanding of relativistic jet behavior near supermassive black holes.

Contribution

It offers the first detailed, multi-year VLBA observational analysis of M87's inner jet structure and dynamics, including apparent motions and acceleration patterns.

Findings

Jet speeds range from 0 to over 2c.

Acceleration occurs within the first 3 milliarcseconds.

Jet exhibits side-to-side motion with a 9-year cycle.

Abstract

M87 is the best source in which to study a jet at high resolution in gravitational units because it has a very high mass black hole and is nearby. The angular size of the black hole is second only to Sgr A*, which does not have a strong jet. The jet structure is edge brightened with a wide opening angle base and a weak counterjet. We have roughly annual observations for 17 years plus intensive monitoring at three week intervals for a year and five day intervals for 2.5 months made with the Very Long Baseline Array (VLBA) at 43 GHz. The inner jet shows very complex dynamics, with apparent motions both along and across the jet. Speeds from zero to over 2c are seen, with acceleration observed over the first 3 milli-arcseconds. The counterjet decreases in brightness much more rapidly than the main jet, as is expected from relativistic beaming in an accelerating jet oriented near the line-of-sight. Details of the structure and dynamics are discussed. The roughly annual observations show side-to-side motion of the whole jet with a characteristic time scale of about 9 years.