Gravitational Wave Research Gives Insights Into Galaxy Evolution And Mergers

In a new study, experts get an insight into the astrophysically significant limits in the search for low-frequency gravitational waves, with information from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). It sheds light on the nature of galaxy evolution, as well as the frequency of mergers.

The NANOGrav's dataset, collected over nine years, was examined, after a campaign was conducted by the Green Bank Telescope in West Virginia and the Arecibo Observatory in Puerto Rico, two of the "most sensitive radio telescopes on Earth."

The study revealed "constraining limits" on the existence of supermassive black hole binaries, which indicate that they are fewer than we thought. This theory can bring about a change in our perception of the galaxy and black hole evolution.

Black hole binaries in galaxies of the sky emit low-frequency gravitational waves but are tough to identify. Pulsars are radio waves at the core of massive stars that remain after stars go supernova. The speediest pulsars emit a pulse every few milliseconds. These "millisecond pulsars" (MSPs) are said to the most precise ways of identifying tiny gravitational wave signals.

"This measurement is possible because the gravitational wave background imprints a unique signature onto the radio waves seen from a collection of MSPs," said Justin Ellis, co-author of the study and researcher from the California Institute of Technology in Pasadena, Calif.

Hence, the data can help astrophysicists to employ computer modeling and understand how often galaxies merge, forming supermassive black hole binaries,helping us to understand the evolution of these astrophysical phenomena.

"After nine years of observing a collection of MSPs, we haven't detected the stochastic background but we are beginning to rule out many predictions based on current models of galaxy evolution," Ellis said. "We are now at a point where the non-detection of gravitational waves is actually improving our understanding of black hole binary evolution."

"Pulsar timing arrays like NANOGrav is said Scott Ransom, co-author of the study, from the NRAO in Charlottesville, Va. "As we improve our detection capabilities, we get closer and closer to that important threshold where the cosmic murmur begins to be heard. At that point, we'll be able to perform entirely new types of physics experiments on cosmic scales and open up a new window on the universe, just like LIGO just did for high-frequency gravitational waves."

The findings were published in the April 4 issue of The Astrophysical Journal.