A high-energy gamma-ray flare from the super-massive black hole in the Messier 87 (M87) galaxy was observed in 2018 for the first time in nearly a decade, thanks to an international effort involving McGill University researchers. This discovery has yielded important insights into the physics of black hole jets, which are among the most efficient engines for distributing energy from the inside of a galaxy to the expanse of the Universe.
Daryl Haggard, a professor in the Department of Physics and a co-coordinator of the Event Horizon Telescope (EHT) multi-wavelength science working group, played a key role in analyzing data from the 2018 observational campaign. That analysis, over a period of several years, allowed researchers to understand they had observed a gamma-ray flare for the first time since 2010. They published their findings this week in Astronomy & Astrophysics.
Image by EHT Collaboration, Fermi-LAT Collaboration, H.E.S.S. Collaboration, MAGIC Collaboration, VERITAS Collaboration, EAVN Collaboration.
"In the first image obtained during the 2018 observational campaign, we saw that the emission along the ring was not homogeneous; instead, it showed asymmetries (i.e., brighter areas)," Haggard said. "Subsequent observations conducted in 2018 and related to this paper confirmed that finding, highlighting that the asymmetry's position angle had changed."
Led by Giacomo Principe, a researcher at the University of Trieste, the study recorded data across the electromagnetic spectrum from X-rays to radio waves using over 25 observatories. These included NASA's Fermi Gamma-ray Space Telescope, Chandra X-ray Observatory and three advanced imaging atmospheric Cherenkov telescope arrays, including VERITAS which has substantial McGill participation.
The flare, which lasted three days, originated from a compact region near the black hole's event horizon, measuring less than three light-days across. This high-energy activity, paired with evolving observations of the black hole's ring, revealed critical connections between the black hole and its relativistic jets, powerful streams of particles.
"Observations both recent ones with a more sensitive EHT array and those planned for the coming years will provide invaluable insights and an extraordinary opportunity to study the physics surrounding M87's supermassive black hole," said Principe.
Located 55 million light-years away in the Virgo galaxy cluster, M87's black hole has a mass 6.5 billion times that of the sun. Its relativistic jets serve as natural laboratories for studying how particles are accelerated to near-light speeds.
"How and where particles are accelerated in supermassive black hole jets is a long-standing mystery," said Sera Markoff, a professor at the University of Amsterdam and co-coordinator of the EHT multi-wavelength working group. "For the first time, we can combine direct imaging of the near event horizon regions during gamma-ray flares caused by particle acceleration events and thus test theories about the flare origins."
About the study
"Broadband Multi-wavelength Properties of M87 during the 2018 EHT Campaign including a Very High Energy Flaring Episode", by The Event Horizon Telescope- Multi-wavelength science working group, The Event Horizon Telescope Collaboration, The Fermi Large Area Telescope Collaboration, H.E.S.S. Collaboration, MAGIC Collaboration, VERITAS Collaboration, and EAVN Collaboration. In: Astronomy & Astrophysics.
Contributing co-authors from McGill include Professor Daryl Haggard; Professor Ken Ragan; Stephan O'Brien, PhD; Hope Boyce, PhD and PhD-candidates Nicole Ford, Matthew Lundy and Samantha Wong.
McGill researchers' contributions have been supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Government of Canada Research Chair's program, the Fonds de recherche du Québec Nature and Technologies (FRQNT), particularly through the Centre de recherche en astrophysique du Québec (CRAQ), the Digital Research Alliance of Canada (DRAC), including Compute Ontario (http://computeontario.ca) and Calcul Quebec (http://www.calculquebec.ca), and the Arthur B. McDonald Canadian Astroparticle Physics Research Institute.
