A rapidly growing supermassive black hole — known as an active galactic nucleus — in the center of a distant galaxy appears to have consumed large amounts of gas while blasting off an outflow of high-energy particles. The outflow eventually switched off then turned back on about 100,000 years later.
This image shows the SDSS J1354+1327 galaxy in a composite image with data from Chandra (purple), and Hubble (red, green and blue). The inset box contains a close-up view of the central region around SDSS J1354+1327’s supermassive black hole. The larger companion galaxy, SDSS J1354+1328, is shown to the north. Image credit: NASA / CXC / University of Colorado / STScI/ J. Comerford et al.
The supermassive black hole under study is located in a galaxy called SDSS J1354+1327 (J1354 for short), which is approximately 900 million light-years from Earth.
Dr. Julie Comerford from the University of Colorado at Boulder and colleagues used observations from NASA’s Chandra X-ray Observatory and the NASA/ESA Hubble Space Telescope, as well as the W.M. Keck Observatory in Mauna Kea, Hawaii, and the Apache Point Observatory near Sunspot, New Mexico.
Chandra detected a bright, point-like source of X-ray emission from J1354, a telltale sign of the presence of an extremely massive black hole.
The X-rays are produced by gas heated to millions of degrees by the enormous gravitational and magnetic forces near the black hole. Some of this gas will fall into the black hole, while a portion will be expelled in a powerful outflow of high-energy particles.
By comparing images from Chandra and Hubble, the astronomers determined that the black hole is located in the center of the galaxy, the expected address for such an object.
The X-ray data also show that the supermassive black hole is embedded in a heavy veil of gas.
The optical data indicate that, in the past, the supermassive black hole appears to have consumed, or accreted, large amounts of gas while blasting off an outflow of high-energy particles. The outflow eventually switched off then turned back on about 100,000 years later.
This is strong evidence that accreting black holes can switch their power output off and on again over timescales that are short compared to the 13.8 billion-year age of the Universe.
“We are seeing this object feast, burp and nap, and then feast and burp once again, which theory had predicted,” Dr. Comerford said.
“Fortunately, we happened to observe this galaxy at a time when we could clearly see evidence for both events.”
So why did the black hole have two separate meals? The answer lies in a companion galaxy that is linked to J1354 by streams of stars and gas produced by a collision between the two galaxies.
Dr. Comerford and co-authors concluded that clumps of material from the companion galaxy swirled toward the center of J1354 and then were eaten by the supermassive black hole.
They used optical data from Hubble, Keck and the Apache Point Observatory to show that electrons had been stripped from atoms in a cone of gas extending some 30,000 light-years south from the galaxy’s center.
This stripping was likely caused by a burst of radiation from the vicinity of the black hole, indicating that a feasting event had occurred.
To the north they found evidence for a shock wave, similar to a sonic boom, located about 3,000 light years from the black hole. This suggests that a burp occurred after a different clump of gas had been consumed roughly 100,000 years later.
“This galaxy really caught us off guard,” said co-author Rebecca Nevin, a doctoral student at the University of Colorado at Boulder.
“We were able to show that the gas from the northern part of the galaxy was consistent with an advancing edge of a shock wave, and the gas from the south was consistent with an older outflow from the black hole.”
A paper on the subject was published in the November 6, 2017 issue of the Astrophysical Journal and is available online at arXiv.org.
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Julia M. Comerford et al. 2017. An Active Galactic Nucleus Caught in the Act of Turning Off and On. ApJ 849, 102; doi: 10.3847/1538-4357/aa8e4b
