Mapping Magnetic Fields with INterferometry Down to Event hoRizon Scales

Active galactic nuclei (AGN) are the most extreme sources of radiative and kinetic power in the Universe, often outshining their entire host galaxies.

The production and outward transport of the AGN power can be explained involving rotating supermassive black holes, accretion disks, relativistic plasma jets, and magnetic fields.

These plasma jets have been imaged on scales from a few light-days up to thousands of light-years using Very Long Baseline Interferometry (VLBI).

The Event Horizon Telescope Collaboration (EHT) has succeeded in imaging the putative super-massive black hole in the galaxy M87 on event horizon scales with sufficient sensitivity and resolution to confirm theoretical predictions derived from General Relativity.

However, to ultimately establish the existence of such black holes and to determine their physical properties, precise information is needed about the magnetic field near the event horizon, where it reflects the fundamental black hole physics and governs the formation of the relativistic jets. Such measurements pose tremendous challenges and cannot be realised merely from improvements of the EHT imaging.

M2FINDERS will meet this technical and astronomical challenge and precisely map magnetic fields at distances smaller than 1000 gravitational radii.

To achieve this ambitious goal, I will combine multi-frequency polarimetric VLBI imaging and opacity measurements with novel methods for image analysis and modelling of relativistic flows.

Leveraging the recent major advances in VLBI instrumentation, I will undertake an observational program that will result in the most stringent constraints on the strength and structure of the magnetic field near the event horizon.

This will provide crucial independent evidence, complementary to EHT imaging, for the existence of black holes and their event horizons.