Supermassive black holes have long been considered a critical element in the formation and evolution of galaxies. However, outside the local Universe, measuring the mass of these cosmic behemoths has remained a challenge, as it is typically only possible for those in an active state. This limitation has restricted sample sizes and introduced selection biases.
A breakthrough has now been made in the study of black holes, thanks to gravitational lensing. This phenomenon occurs when a foreground galaxy bends and magnifies the light from a more distant object, allowing for the measurement of a supermassive black hole’s mass. James Nightingale, an astronomer from Durham University, explains that most of the largest known black holes are in an active state, emitting light, X-rays, and other radiation. However, gravitational lensing has made it possible to study inactive black holes in distant galaxies, an otherwise unattainable goal.
Using gravitational lensing and supercomputer simulations on the DiRAC HPC facility, Nightingale and his team were able to examine how light is bent by a supermassive black hole inside Abell 1201 BCG. This groundbreaking technique involves simulating light traveling through the Universe hundreds of thousands of times, with each simulation incorporating a different mass black hole to alter light’s journey to Earth.
When the researchers included an ultramassive black hole in one of their simulations, the path is taken by the light from the faraway galaxy to reach Earth corresponded to the path seen in actual images captured by the NASA/ESA Hubble Space Telescope. This black hole, estimated to be approximately 30 billion times the mass of our Sun, is one of the largest ever detected and sits at the upper limit of what is theoretically believed to be possible. Nightingale describes the discovery as “extremely exciting.”
The team’s findings have been published in a paper in the Monthly Notices of the Royal Astronomical Society. This new approach using gravitational lensing and supercomputer simulations could pave the way for detecting many more black holes beyond our local Universe, offering crucial insights into the evolution of these enigmatic cosmic entities throughout time.
J.W. Nightingale et al. 2023. Abell 1201: detection of an ultramassive black hole in a strong gravitational lens. MNRAS 521 (3): 3298-3322; doi: 10.1093/mnras/stad587