Multiwavelength View of the M87 Black Hole Captured by the Event Horizon Telescope

TL;DR

This paper discusses the 2017 EHT imaging of M87's black hole and a comprehensive multi-wavelength campaign revealing the galaxy's low activity state and detailed spectrum of its core.

Contribution

It provides the first simultaneous multi-wavelength spectrum of M87's nucleus and correlates EHT imaging with multi-band observations.

Findings

M87 was in a historically low activity state.

The most complete simultaneous multi-wavelength spectrum of M87's core was obtained.

X-ray emission from the core dominates over HST-1 during this period.

Abstract

In 2017, the first image of the center of the M87 galaxy was captured by the Event Horizon Telescope (EHT). It revealed a ring morphology and a size consistent with theoretical expectations for the light pattern around a weakly accreting supermassive black hole of ~6.5 billion solar masses. In parallel to the EHT measurements, an extensive multi-wavelength (MWL) campaign with ground- and space-based facilities from radio all the way up to the TeV energy range was organized. In this note we will give an overview of the results from this campaign. M87 was found to be in a historically low state. At X-ray energies the emission from the core dominates over HST-1. We present the most complete simultaneous, MWL spectrum of the active nucleus to date.