UMBC researchers identify where giant jets from black holes discharge their energy

December 15, 2020

The supermassive black holes at the centers of galaxies are the most massive objects in the universe. They range from about 1 million to upwards of 10 billion times the mass of the Sun. Some of these black holes also blast out gigantic, super-heated jets of plasma at nearly the speed of light. The primary way that the jets discharge this powerful motion energy is by converting it into extremely high-energy gamma rays. However, UMBC physics Ph.D. candidate Adam Leah Harvey says, "How exactly this radiation is created is an open question."

The jet has to discharge its energy somewhere, and previous work doesn't agree where. The prime candidates are two regions made of gas and light that encircle black holes, called the broad-line region and the molecular torus.

A black hole's jet has the potential to convert visible and infrared light in either region to high-energy gamma rays by giving away some of its energy. Harvey's new NASA-funded research sheds light on this controversy by offering strong evidence that the jets mostly release energy in the molecular torus, and not in the broad-line region. The study was Nature Communications and co-authored by UMBC physicists Markos Georganopoulos and Eileen Meyer.

Far out

The broad-line region is closer to the center of a black hole, at a distance of about 0.3 light-years. The molecular torus is much farther out--more than 3 light-years. While all of these distances seem huge to a non-astronomer, the new work "tells us that we're getting energy dissipation far away from the black hole at the relevant scales," Harvey explains.

"The implications are extremely important for our understanding of jets launched by black holes," Harvey says. Which region primarily absorbs the jet's energy offers clues to how the jets initially form, pick up speed, and become column-shaped. For example, "It indicates that the jet is not accelerated enough at smaller scales to start to dissipate energy," Harvey says.

Other researchers have proposed contradictory ideas about the jets' structure and behavior. Because of the trusted methods Harvey used in their new work, however, they expect the results to be broadly accepted in the scientific community. "The results basically help to constrain those possibilities--those different models--of jet formation."

On solid footing

To come to their conclusions, Harvey applied a standard statistical technique called "bootstrapping" to data from 62 observations of black hole jets. "A lot of what came before this paper has been very model-dependent. Other papers have made a lot of very specific assumptions, whereas our method is extremely general," Harvey explains. "There isn't much to undermine the analysis. It's well-understood methods, and just using observational data. So the result should be correct."

A quantity called the seed factor was central to the analysis. The seed factor indicates where the light waves that the jet converts to gamma rays come from. If the conversion happens at the molecular torus, one seed factor is expected. If it happens at the broad-line region, the seed factor will be different.

Georganopolous, associate professor of physics and one of Harvey's advisors, originally developed the seed factor concept, but "applying the idea of the seed factor had to wait for someone with a lot of perseverance, and this someone was Adam Leah," Georganopolous says.

Harvey calculated the seed factors for all 62 observations. They found that the seed factors fell in a normal distribution aligned almost perfectly around the expected value for the molecular torus. That result strongly suggests that the energy from the jet is discharging into light waves in the molecular torus, and not in the broad-line region.

Tangents and searches

Harvey shares that the support of their mentors, Georganopoulos and Meyer, assistant professor of physics, was instrumental to the project's success. "I think that without them letting me go off on a lot of tangents and searches of how to do things, this would have never gotten to the level that it's at," Harvey says. "Because they allowed me to really dig into it, I was able to pull out a lot more from this project."

Harvey identifies as an "observational astronomer," but adds, "I'm really more of a data scientist and a statistician than I am a physicist." And the statistics has been the most exciting part of this work, they say.

"I just think it's really cool that I was able to figure out methods to create such a strong study of such a weird system that is so removed from my own personal reality." Harvey says. "It's going to be fun to see what people do with it."
-end-
Please bold subheadings: Far out On solid footing Tangents and searches

Please hyperlink in graf 2, "published in Nature Communications":

University of Maryland Baltimore County

Related Black Holes Articles from Brightsurf:

The black hole always chirps twice: New clues deciphering the shape of black holes
A team of gravitational-wave scientists led by the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) reveal that when two black holes collide and merge, the remnant black hole 'chirps' not once, but multiple times, emitting gravitational waves--intense ripples in the fabric space and time--that inform us about its shape.

Black holes? They are like a hologram
Spherical, smooth and simple according to the theory of relativity, or extremely complex and full of information as, according to quantum laws, Stephen Hawking used to say?

Under pressure, black holes feast
A new, Yale-led study shows that some supermassive black holes actually thrive under pressure.

Staining cycles with black holes
In the treatment of tumors, microenvironment plays an important role.

Black holes sometimes behave like conventional quantum systems
A group of Skoltech researchers led by Professor Anatoly Dymarsky have studied the emergence of generalized thermal ensembles in quantum systems with additional symmetries.

Scientists may have discovered whole new class of black holes
New research shows that astronomers' search for black holes might have been missing an entire class of black holes that they didn't know existed.

Are black holes made of dark energy?
Two University of Hawaii at Manoa researchers have identified and corrected a subtle error that was made when applying Einstein's equations to model the growth of the universe.

Telescopes in space for even sharper images of black holes
Astronomers have just managed to take the first image of a black hole, and now the next challenge facing them is how to take even sharper images, so that Einstein's Theory of General Relativity can be tested.

Can entangled qubits be used to probe black holes?
Information escapes from black holes via Hawking radiation, so it should be possible to capture it and use it to reconstruct what fell in: if given time longer than the age of the universe.

How black holes power plasma jets
Cosmic robbery powers the jets streaming from a black hole, new simulations reveal.

Read More: Black Holes News and Black Holes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.