The Jet in M87 from e-EVN Observations

TL;DR

This study uses e-EVN radio observations to analyze the jet structure and dynamics of M87, correlating jet activity with high-energy gamma-ray flares, revealing changes in jet velocity over time.

Contribution

First multi-epoch e-EVN observations of M87 during gamma-ray activity, linking jet kinematics with high-energy flares and identifying velocity changes around 2005.5.

Findings

Detection and resolution of the inner jet and HST-1.

Observation of a velocity change in HST-1 around 2005.5.

Correlation between jet activity and gamma-ray flares.

Abstract

One of the most intriguing open questions of today's astrophysics is the one concerning the location and the mechanisms for the production of MeV, GeV, and TeV gamma-rays in AGN jets. M87 is a privileged laboratory for a detailed study of the properties of jets, owing to its proximity, its massive black hole, and its conspicuous emission at radio wavelengths and above. We started on November 2009 a monitoring program with the e-EVN at 5 GHz, during which two episodes of activity at energy E > 100 GeV have occured. We present here results of these multi-epoch observations. The inner jet and HST-1 are both detected and resolved in our datasets. One of these observations was obtained at the same day of the first high energy flare. A clear change in the proper motion velocity of HST-1 is present at the epoch ~2005.5. In the time range 2003 -- 2005.5 the apparent velocity is subluminal, and superluminal (~ 2.7c) after 2005.5.