Galaxy Returns To The Shadows After Black Hole Activity Ceases

ESO's Very Large Telescope image of Markarian 1018. ESO/CARS survey

Supermassive black holes tend to sit quietly at the core of galaxies for million of years. But if material falls towards them they can end up in a feeding frenzy, emitting so much light that they outshine their host galaxies. A new study provides the most detailed look yet at this whole cycle.

An international team of astronomers observed the galaxy Markarian 1018, 578 million light-years away, going back to its dim original state after just 30 years of activity from its supermassive black hole. Such a quick turnaround is a heartbeat in cosmic terms.

“We were stunned to see such a rare and dramatic change in Markarian 1018,” said lead author Rebecca McElroy, a PhD student at the University of Sydney, in a statement.

The serendipitous discovery was possible thanks to the European Southern Observatory (ESO), which is keeping tabs on 40 active galaxies including Markarian 1018. In a paper, published in Astronomy & Astrophysics, the team reports that the fading has only recently started.

“We were lucky that we detected the event just 3-4 years after the decline started so we could begin monitoring campaigns to study details of the accretion physics of active galaxies that cannot be studied otherwise,” commented project leader Bernd Husemann, author of a supporting paper also published in Astronomy & Astrophysics. “The team had to work fast to determine what was causing Markarian 1018’s return to the shadows.”

The team was able to make the most of this discovery, looking at the object with many different instruments like the Hubble Space Telescope and the Chandra X-ray Observatory. Thanks to the extra data, the astronomers discovered that the supermassive black hole was being slightly deprived of gas.

“It’s possible that this starvation is because the inflow of fuel is being disrupted,” continued McElroy. “An intriguing possibility is that this could be due to interactions with a second supermassive black hole.”

The galaxy is the result of a major merger event, so a second black hole stealing gas is a likely explanation for Markarian 1018. ESO and other facilities will continue to observe this peculiar object.

Black hole accretion is a key feature in galaxy evolution, and thanks to these new observations, we now have new a fresh insight into it.


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