̽��ֱ�� of Cambridge - quasar

Chandra Observatory shows black hole spins slower than its peers

sc604 — Thu, 30 Jun 2022 16:10:01 +0000

Supermassive black holes contain millions or even billions of times more mass than the Sun. Astronomers think that nearly every large galaxy has a supermassive black hole at its center. While the existence of supermassive black holes is not in dispute, scientists are still working to understand how they grow and evolve. One critical piece of information is how fast the black holes are spinning.

“Every black hole can be defined by just two numbers: its spin and its mass,” said Julia Sisk-Reynes of Cambridge's Institute of Astronomy (IoA), who led the study, published in the Monthly Notices of the Royal Astronomical Society. “While that sounds fairly simple, figuring those values out for most black holes has proved to be incredibly difficult.”

For this result, researchers observed X-rays that bounced off a disk of material swirling around the black hole in a quasar known as H1821+643. Quasars contain rapidly growing supermassive black holes that generate large amounts of radiation in a small region around the black hole. Located in a cluster of galaxies about 3.4 billion light-years from Earth, H1821+643’s black hole is between about three and 30 billion solar masses, making it one of the most massive known. By contrast, the supermassive black hole in the center of our galaxy weighs about four million Suns.

̽��ֱ��strong gravitational forces near the black hole alter the intensity of X-rays at different energies. ̽��ֱ��larger the alteration the closer the inner edge of the disk must be to the point of no return of the black hole, known as the event horizon. Because a spinning black hole drags space around with it and allows matter to orbit closer to it than is possible for a non-spinning one, the X-ray data can show how fast the black hole is spinning.

“We found that the black hole in H1821+643 is spinning about half as quickly as most black holes weighing between about a million and ten million suns,” said co-author Professor Christopher Reynolds, also of the IoA. “ ̽��ֱ��million-dollar question is: why?”

̽��ֱ��answer may lie in how these supermassive black holes grow and evolve. This relatively slow spin supports the idea that the most massive black holes like H1821+643 undergo most of their growth by merging with other black holes, or by gas being pulled inwards in random directions when their large disks are disrupted.

Supermassive black holes growing in these ways are likely to often undergo large changes of spin, including being slowed down or wrenched in the opposite direction. ̽��ֱ��prediction is therefore that the most massive black holes should be observed to have a wider range of spin rates than their less massive relatives.

On the other hand, scientists expect less massive black holes to accumulate most of their mass from a disk of gas spinning around them. Because such disks are expected to be stable, the incoming matter always approaches from a direction that will make the black holes spin faster until they reach the maximum speed possible, which is the speed of light.

“ ̽��ֱ��moderate spin for this ultramassive object may be a testament to the violent, chaotic history of the universe’s biggest black holes,” said co-author Dr James Matthews, also of the IoA. “It may also give insights into what will happen to our galaxy’s supermassive black hole billions of years in the future, when the Milky Way collides with Andromeda and other galaxies.

This black hole provides information that complements what astronomers have learned about the supermassive black holes seen in our galaxy and in M87, which were imaged with the Event Horizon Telescope. In those cases, the black hole’s masses are well known, but the spin is not.

NASA's Marshall Space Flight Center manages the Chandra program. ̽��ֱ��Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.

Reference:
Júlia Sisk-Reynés et al. 'Evidence for a moderate spin from X-ray reflection of the high-mass supermassive black hole in the cluster-hosted quasar H1821+643.' Monthly Notices of the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac1389

Adapted from a Chandra press release.

Astronomers have made a record-breaking measurement of a black hole’s spin, one of two fundamental properties of black holes. NASA’s Chandra X-ray Observatory shows this black hole is spinning slower than most of its smaller cousins. This is the most massive black hole with an accurate spin measurement and gives hints about how some of the universe’s biggest black holes grow.

̽��ֱ��moderate spin for this ultramassive object may be a testament to the violent, chaotic history of the universe’s biggest black holes

James Matthews

X-ray: NASA/CXC/Univ. of Cambridge/J. Sisk-Reynés et al.; Radio: NSF/NRAO/VLA; Optical: PanSTARRS

H1821+643, a quasar powered by a supermassive black hole

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Galactic ‘hailstorm’ in the early Universe

sc604 — Fri, 16 Jan 2015 06:00:53 +0000

Two teams of astronomers led by researchers at the ̽��ֱ�� of Cambridge have looked back nearly 13 billion years, when the Universe was less than 10 percent its present age, to determine how quasars – extremely luminous objects powered by supermassive black holes with the mass of a billion suns – regulate the formation of stars and the build-up of the most massive galaxies.

Using a combination of data gathered from powerful radio telescopes and supercomputer simulations, the teams found that a quasar spits out cold gas at speeds up to 2000 kilometres per second, and across distances of nearly 200,000 light years – much farther than has been observed before.

How this cold gas - the raw material for star formation in galaxies - can be accelerated to such high speeds had remained a mystery. Detailed comparison of new observations and supercomputer simulations has only now allowed researchers to understand how this can happen: the gas is first heated to temperatures of tens of millions of degrees by the energy released by the supermassive black hole powering the quasar. This enormous build-up of pressure accelerates the hot gas and pushes it to the outskirts of the galaxy.

̽��ֱ��supercomputer simulations show that on its way out of the parent galaxy, there is just enough time for some of the hot gas to cool to temperatures low enough to be observable with radio telescopes. ̽��ֱ��results are presented in two separate papers published today (16 January) in the journals Monthly Notices of the Royal Astronomical Society and Astronomy & Astrophysics.

Quasars are amongst the most luminous objects in the Universe, and the most distant quasars are so far away that they allow us to peer back billions of years in time. They are powered by supermassive black holes at the centre of galaxies, surrounded by a rapidly spinning disk-like region of gas. As the black hole pulls in matter from its surroundings, huge amounts of energy are released.

“It is the first time that we have seen outflowing cold gas moving at these large speeds at such large distances from the supermassive black hole,” said Claudia Cicone, a PhD student at Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology, and lead author on the first of the two papers. “It is very difficult to have matter with temperatures this low move as fast as we observed.”

Cicone’s observations allowed the second team of researchers specialising in supercomputer simulations to develop a detailed theoretical model of the outflowing gas around a bright quasar.

“We found that while gas is launched out of the quasar at very high temperatures, there is enough time for some of it to cool through radiative cooling – similar to how the Earth cools down on a cloudless night,” said Tiago Costa, a PhD student at the Institute of Astronomy and the Kavli Institute for Cosmology, and lead author on the second paper. “ ̽��ֱ��amazing thing is that in this distant galaxy in the young Universe the conditions are just right for enough of the fast moving hot gas to cool to the low temperatures that Claudia and her team have found.”

Working at the IRAM Plateau De Bure interferometer in the French Alps, the researchers gathered data in the millimetre band, which allows observation of the emission from the cold gas which is the primary fuel for star formation and main ingredient of galaxies, but is almost invisible at other wavelengths.

̽��ֱ��research was supported by the UK Science and Technology Facilities Council (STFC), the Isaac Newton Trust and the European Research Council (ERC). ̽��ֱ��computer simulations were run using the Computer Cluster DARWIN, operated by the ̽��ֱ�� of Cambridge High Performance Computing Service, as part of STFCs DiRAC supercomputer facility.

Inset image: Comparison of observation and simulations. Credit: Tiago Costa

Astronomers have been able to peer back to the young Universe to determine how quasars – powered by supermassive black holes with the mass of a billion suns – form and shape the evolution of galaxies.

While gas is launched out of the quasar at very high temperatures, there is enough time for some of it to cool through radiative cooling – similar to how the Earth cools down on a cloudless night

Tiago Costa

Illustration of the outflow (red) and gas flowing in to the quasar in the centre (blue). ̽��ֱ��cold clumps shown in the inset image are expelled out of the galaxy in a 'galactic hailstorm'

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