The supermassive black hole powering M87's core has a mass about 6.5 billion times that of the Sun and generates two jets of plasma that extend thousands of light-years in opposite directions. The jet oriented toward Earth exibits notable luminosity and appears with a blue tint due to the relativistic effect called "Doppler boosting", which occurs when particles are accelerated by the black hole up to 99% of the speed of light. As these particles travel toward the observer, the relativistic effects compress the emitted photons' wavelengths, shifting their energies into the blue portion of the electromagnetic spectrum. Conversely, the same effect causes the counterjet, which is moving away from us, to appear redder and dimmer in luminosity.

We have imaged M87 using RGB broadband filters (Astrodon Gen2 I-series RGB) with a Meade LX200 ACF 10” and a QHY268m imaging camera. We have obtained an integrated image for each color filter by stacking 250 subexposures of 300 seconds each. To reveal faint details overshadowed by this bright galaxy, we subtracted a realistic model of M87 - created using a two dimensional parametric fitting algorithm (GALFIT v.3) - from all three integrated images.

After subtraction, apart from the famous bright blue jet and numerous globular cluster candidates, some non-stellar emission features became evident in all wavelengths, with the brightest appearing in the red filter window (590 nm to 700 nm).  
These structures, along with dark dust lanes, are not artifacts generated by the galaxy subtraction process but are real features. Those near the M87 core have been previously imaged by the Hubble Space Telescope in a narrower field of view. According to the literature, these features could potentially be structures related to the counterjet, such as counterjet-generated shockfront.
To the best of our knowledge this is the first wide field, galaxy-subtracted broadband RGB image of M87.
Publication is pending.

Authors: Attilio Bruzzone and Antonio Ferretti - Gruppo Astrofili Frentani

March-April 2024