(CN) – Astronomers using the 8-meter Gemini North telescope atop Hawaii’s Mauna Kea have probed what they describe as “an enigmatic and unexpected supermassive black hole dominating the core of a large galaxy in the cosmic backwaters.”
“It’s a bit like finding a skyscraper in a Kansas wheat field, rather than in Manhattan,” University of California Berkley astronomer Chung-Pei Ma, who led the international team of researchers that made the discovery, said.
“We expect to find gigantic black holes in massive galaxies in a crowded region of the universe, where frequent galaxy collisions and cannibalism sustain the black holes’ insatiable appetite and allow them to grow to excess. But to find one in relative isolation indicates that the black hole has long ago tapped its sources of matter that allowed it to grow,” Ma said.
The research, published online on April 6 in the journal Nature, provides a rare glimpse of a supermassive black hole – one with a mass some 17 billion times the mass of the sun – deep within a rather isolated galaxy known as NGC 1600 some 200 million light years from the Milky Way.
Finding such a monster black hole lurking in a relatively barren cosmic outpost with so few traveling companions is as much an opportunity as it is an enigma. The “lonely monster” is helping to shed light on how huge black holes could have formed rapidly in the early epochs of our universe, the researchers said.
“Other galaxies found to harbor very massive black holes are typically located in dense regions of the universe populated by many other galaxies and clusters,” lead author of the paper Jens Thomas, of the Max Planck Institute of Physics, said. “By contrast, NGC 1600 is in a modest group of galaxies in a rather mundane part of the sky.”
The question researchers have been trying to answer is how can such a large black hole exist now without a substantial source of material to feast on.
“Within the group, NGC 1600 is by far the most brilliant member and outshines other members by at least three times, an indication that NGC 1600 may have cannibalized its former neighboring galaxies and their central black holes in its youth,” Thomas said.
“NGC 1600 also appears to have scoured away many of its central stars,” Thomas added. He believes that the black hole within NGC 1600 was once part of a pair or even several black holes that worked as a team to gravitationally expel nearby stars.
“Rather than devour them, the black holes would act like a gravitational slingshot, sending neighboring stars careening out of the galaxy’s core, Thomas said.
Understanding this lonely relic galaxy required the power of the Gemini Multi-Object Spectrograph on the Gemini North 8-meter telescope on Mauna Kea in Hawaii. The telescope allowed the team to discover the extreme mass of the black hole, map its environment and model and analyze the data.
“After many years of exemplary service, it’s great to see that the Gemini Multi-Object Spectrographs continue to contribute in such a fundamental way to these important areas of astronomy,” Chris Davis, program director at the U.S. National Science Foundation, said. The foundation, together with partner agencies in Argentina, Brazil, Canada, and Chile, support the operation of the Gemini Observatory.
“In just a few months, two separate teams using [the Gemini telescope] have published compelling yet contrasting results: one group finding evidence for a supermassive black hole that’s flinging stars outward from its galaxy’s core, and another observing a black hole that clings on to its stellar neighbors,” Davis added. “One wonders what other remarkable things Gemini and this remarkable technology will tell us about super-massive black holes and the cores of distant galaxies in the years to come.”
The focus on NGC 1600 for this study was a result of the MASSIVE Survey, supported by the foundation. Initiated in 2014, the MASSIVE Survey focuses on about 100 of the most massive, early-type, galaxies within about 300 million light years of the Milky Way. Gemini continues to play a critical role in MASSIVE by measuring the velocities of stars swarming around the galaxies’ supermassive black holes, and thus discovering the black holes’ masses.
Ma speculates that NGC 1600’s black hole might be the tip of an iceberg.
“Maybe there are many more monster black holes that don’t live in an obvious skyscraper in Manhattan,” Ma said. She also notes that the masses of the three largest known black holes were all determined by Gemini, including two 10-billion-solar-mass black holes discovered by her team in 2011.
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