Simulations created by Associate Professor Chris Richardson have helped reveal elusive black holes observed with the James Webb Space Telescope
Supermassive black holes, millions to billions of times the mass of the Sun, lie at the center of all large galaxies like the Milky Way. How these supermassive black holes became supermassive remains an unsolved question, but astronomers know these black holes play a crucial role in how their host galaxies evolve. To understand black hole evolution, astronomers must identify intermediate-mass black holes (IMBHs), which are much less massive than the supermassive variety. Unfortunately, IMBHs are challenging to detect and therefore relatively rare compared to black holes in other mass regimes.
However, in certain situations, an IMBH in a galaxy can leave an imprint of its presence in the light emitted by the gas surrounding it. This spectrum of light can encode much information about the black hole, including its mass. Chris Richardson, associate professor of astrophysics at Elon University, created a suite of simulations in a paper published in 2022 that predicted what we would see from the James Webb Space Telescope if IMBHs were active in dwarf galaxies, which are much smaller than the Milky Way.
Two recent papers in which Richardson is a co-author have used these simulations to interpret their JWST observations of two dwarf galaxies at vastly different distances in the Universe. The first paper, led by John Chisholm at the University of Texas – Austin, found that Richardson’s models were the only possible explanation for the observed emission they viewed from the galaxy GN 42437 when the Universe was only 1 billion years old. Through various methods, a black hole mass between 100,000 and 10,000,000 times the mass of the Sun was estimated to reside in the galaxy. In a separate paper recently submitted to the Astrophysical Journal, Matilde Mingozzi, at the Space Telescope Science Institute, showed that observations of the dwarf galaxy SBS0335-052 E with JWST were the most consistent with an IMBH about 100,000 times more massive than the Sun. Together, these papers are beginning to pave the way for a new avenue in finding IMBHs, which will help astronomers understand how galaxies like the Milky Way evolved into their current state.