Researchers may have answered a decades-old question about galaxy evolution. They have used the power of artificial intelligence (AI) to accomplish this.
The Hubble Sequence classifies galaxy morphologies. With Hubble’s help, astronomers have been refining our understanding of galaxy evolution and morphology.
By the 1970s, researchers had established that lone galaxies are spiral-shaped. Whereas those found in clusters of galaxies are smooth and featureless. They are known as elliptical and lenticular galaxies (shaped like a lens).
New research led by astronomers at the International Centre for Radio Astronomy Research (ICRAR) was published today in the journal Monthly Notices of the Royal Astronomical Society. In the paper, astronomers claimed that they may have uncovered the reason for these shape differences.
The research, according to lead author Dr. Joel Pfeffer of the ICRAR node at The University of Western Australia, explains the’morphology-density relation. In this relation, clustered galaxies appear smoother and more featureless than their solo counterparts.
“We’ve discovered a few different things happening when we get a lot of galaxies packed together,” Dr. Pfeffer explained.
“The spiral arms of galaxies are extremely fragile. Density increases in galaxy clusters, as spiral galaxies begin to lose gas. Due to the loss of gas, they ‘drop’ their spiral arms. Then they transform into lenticular shapes. Another cause is galaxy mergers can result in two or more spiral galaxies colliding and merging to form one large elliptical galaxy.”
The powerful EAGLE simulations were used to analyse a group of galaxies in detail. Astronomers also used an AI algorithm to classify galaxies based on their shape.
ICRAR Ph.D. candidate Mitchell Cavanagh trained the neural network-based algorithm. It can classify nearly 20,000 galaxies per minute and compress what would normally take weeks into one hour.
The simulations closely match what has been observed in the universe. It gave researchers confidence in using the simulation results to interpret galaxy cluster observations.
The study also discovered several lenticular galaxies outside of the expected high-density regions, with modelling indicating that they were formed by the merger of two galaxies.
According to Dr. Pfeffer, the work brings together various pieces of galactic evolution research to understand the morphology-density relationship for the first time.
“There have been many suggestions over time,” he said. “However, this is the first work to truly put all of the puzzle pieces together.”