Black hole : Radio signals unveil secrets of massive galaxies

An investigation headed by Associate Professor Michael Brown of Monash University’s School of Physics and Astronomy focused on black holes, the cosmic monsters responsible for some of the universe’s brightest radio wave sources.

The state-of-the-art Australian Square Kilometer Array Pathfinder (ASKAP) was employed by the researchers to explore the mysteries of radio waves released by the most massive black holes.

Although the research team acknowledged that radio waves can also be produced by new star formation in galaxies, they concentrated on galaxies that had little to no star formation. All 40 of the largest galaxies analyzed out of the 587 nearby galaxies that were studied were found to emit radio waves.

“While it’s possible there’s some low-level star formation hidden in these galaxies, black holes seem the most likely cause for what we are seeing,” Brown stated.

The research additionally demonstrated differences in radio wave emission between the largest galaxies, some of which turned out to be noticeably more potent than others. As an example, the radio brightness of galaxy ESO 137-G 6 was about 10,000 times higher than that of galaxy NGC 6876.

Under the constraints of Melbourne’s COVID lockdowns, preliminary work on this study was conducted by undergraduate student Teagan Clarke as part of Monash’s physics and astronomy research project unit.

“We’ve been able to really dig into this new data to start to uncover the differences in how these galaxies are shining in radio waves,” Teagan explained.

“This could tell us about their central black holes and how they power these massive galaxies.”

Associate Professor Brown stated, “It’s a bit of a puzzle why some galaxies emit far more radio waves than others.”

It is evident, nevertheless, that galaxies with strong radio emission appear to rotate more slowly than equivalent galaxies with weak radio emission. It will be difficult work for me and my students to get to the bottom of this.”