THE IDEA
A team of international astronomers and physicists led by postdoctoral fellow in multi-messenger astrophysics Nihan Pol and Stephen Taylor, assistant professor of physics and astronomy, used realistic simulations of low-frequency gravitational waves to predict that within the next several years astronomers will likely be able to detect and study the most massive black holes in the universe. This work is a foundation for extracting the underlying astrophysics of galaxies and the pairs of supermassive black holes that produce gravitational waves—the stretching and squeezing of spacetime predicted by Einstein’s general theory of relativity—once those waves are detected.
WHY IT MATTERS
The team is looking for signals that have such low frequency that they all pile on top of each other, producing a so-called “background” of gravitational waves, which can take decades to accumulate. As the team waits for the signal to reach its crescendo, they found that this detection will also arrive packaged with more information about the multiple pairs of black holes giving off the low-frequency gravitational waves. “At the moment of the first detection of wave background, we will be able to strongly assert that supermassive black holes are the culprit, and we’ll be able to test models of supermassive black hole evolution and galaxy formation,” Pol said.
WHAT’S NEXT
Taylor and Pol will be joining their colleagues at the North American Nanohertz Observatory for Gravitational Waves and the International Pulsar Timing Array in teasing out this gravitational wave background from the data in the next several years. They will also be conducting a census of the hundreds of thousands of gigantic black holes that contribute to creating the low-frequency gravitational wave signal, hoping to catalog their mass and establish timeframes for when they merge. This information will enhance our understanding of the growth of galaxies and massive black holes. “Initial detection of the low-frequency gravitational wave background will be fantastic,” Taylor said. “Once we get beyond that, the work that Nihan and our team has done will allow us to figure out the properties of the black holes that contribute to the signal and how these gigantic black holes get close together in the first place.”
FUNDING
The NANOGrav project receives support from National Science Foundation Physics Frontiers Center award number 1430284. Taylor received support from NSF grant AST 2007993 and a Dean’s Faculty Fellowship from the College of Arts & Science.
GO DEEPER
The article, “Astrophysics Milestones for Pulsar Timing Array Gravitational Wave Detection” was published in the journal Astrophysical Journal Letters on April 26.