The late stage of the merger process is so elusive because the interacting galaxies kick up a lot of gas and dust, especially in the final, most violent stages of the merger.
A galaxy merger is a slow process lasting more than a billion years as two galaxies, under the inexorable pull of gravity, dance toward each other before finally joining together.
Astronomers suspect that supermassive black holes lurk at the heart of every sizable galaxy, holding the galactic fiber together.
"Both galaxies host supermassive black holes at their center, which will eventually smash together and merge into one larger black hole".
The researchers analyzed 96 galaxies observed at Keck Observatory, and 385 of galaxies from the archive of Hubble.
Research scientist Michael Koss and astronomers from the University of Maryland observed hundreds of galaxies using images from the W.M. Keck Observatory in Hawaii and NASA's Hubble Space Telescope, according to a news release.
"Computer simulations of galaxy smashups show us that black holes grow fastest during the final stages of mergers, near the time when the black holes interact, and that's what we have found in our survey", said Laura Blecha, an assistant professor of physics at the University of Florida and a co-author of the study. A thick curtain of material forms and shields the galaxy nuclei from view in visible light.
"Heavily obscured galaxy nuclei don't have a bright point source in the center like a lot of luminous unobscured supermassive black holes do", said Koss. The findings suggest that such events are more common than astronomers used to think.
One possible explanation for the apparent lack of a link between quasars and merging galaxies is that gas and dust swirling around these galaxies is likely to heavily obscure the black holes.
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This last step helped the researchers confirm that the luminous galactic cores found in their census of dusty interacting galaxies are indeed a signature of rapidly-growing black hole pairs headed for a collision.
Black holes are areas of space-time which are so dense that nothing - whether matter or energy - can escape them.
"The other is idea is that you need galaxy mergers to trigger large growth". When supermassive black holes collide, not only do they create a mega black hole, they can also unleash powerful energy in the form of gravitational waves.
Scientists first detected the shudders in space-time in 2016 and the discovery was hailed the "biggest scientific breakthrough of the century".
The team targeted galaxies with an average distance of 330 million light-years from Earth.
Gravitational waves are considered ripples in this fabric. Gravitational wave detectors tell astronomers what area, and Koss' research tells them whether that object is likely to host a supermassive black hole merger.
A similar result may occur when the Milky Way galaxy will eventually clash with the nearby Andromeda galaxy.
"The images also presage what will likely happen in a few billion years, when our Milky Way galaxy merges with the neighbouring Andromeda galaxy". Her experience in writing also intersects the IT niche, given the fact that she worked as a content editor for firms that produce software for mobile devices.
Credit: M. Koss (Eureka Scientific, Inc.)/NASA/ESA;Keck images: M. Koss (Eureka Scientific, Inc.)/W.M. Right now, hardware is a huge limitation, but, once the James Webb Space Telescope is deployed in 2021, scientists will be able to measure masses, growth rates, and other physical parameters of black hole pairs. Keck AO has imaged the four massive planets orbiting the star HR8799, measured the mass of the giant black hole at the center of our Milky Way Galaxy, discovered new supernovae in distant galaxies, and identified the specific stars that were their progenitors. These direct observations had not been made before.