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Cal Poly Professor On Team That Solved Mystery Around Distant Supermassive Black Hole

Image of galaxy with a supermassive black hole at its coreThis image from the MUSE instrument on ESO’s Very Large Telescope shows the active galaxy Markarian 1018,
which has a supermassive black hole at its core. The faint loops of light around the galaxy
are a result of its interaction and merger with another galaxy in the recent past.
Credit // ESO/CARS survey


SAN LUIS OBISPO — The mystery of a rare change in the behavior of a supermassive black hole at the center of a distant galaxy has been solved by an international team of astronomers that includes Cal Poly’s Vardha Bennert.

It seems that the black hole has fallen on hard times and is no longer being fed enough fuel to make it shine.

Many galaxies are found to have an extremely bright core powered by a supermassive black hole. They are thought to shine so brightly because hot material is glowing fiercely as it falls into the black hole, a process known as accretion.

Image of a galaxy
This image shows the sky around the faint active galaxy Markarian 1018.
The galaxy itself is at the center of the picture.
Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin

Some galaxies have been observed to change their brightness dramatically over the course of only 10 years; a blink of an eye in astronomical terms. However, Markarian 1018, the galaxy in this new study, stands out by having changed a second time, reverting back to its initial, much dimmer classification within the last five years. Only a handful of galaxies have been observed to make this full-cycle change, and never before has one been studied in such detail.

“This was really surprising. We didn’t expect to see Markarian 1018 undergo such a rare shift, returning to the shadows after being a very bright galaxy,” said Bennert, a physics professor at Cal Poly.

The discovery of Markarian 1018’s fickle nature was a chance by-product of the Close AGN Reference Survey, a collaborative project using the European Southern Observatory’s (ESO) Very Large Telescope and led by ESO’s Bernd Husemann.

As luck would have it, Bennert had taken a spectrum in 2009 using the Keck telescope that showed Markarian 1018 still in its bright phase. This turned out to be the last observation taken of the galaxy while it was bright.

Combining ESO’s observations with Bennert’s as well as observations taken with the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory, the team determined that the black hole was slowly fading because it was being starved of accretion material.

“An intriguing possibility is that this could be due to interactions with a second supermassive black hole,” said Rebecca McElroy, lead author of the discovery paper and a doctoral student at the University of Sydney and the ARC Centre of Excellence for All Sky Astrophysics.

Research continues into the mechanisms at work in galaxies such as Markarian 1018 that change their appearance.

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