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06-13-2024

Black holes may ‘talk’ to galaxies through energetic winds

A new study led by the University of Wisconsin–Madison has found that gas clouds in a distant galaxy are being propelled outward at speeds exceeding 10,000 miles per second by radiation from a supermassive black hole at the galaxy’s center. The research suggests that winds from black holes influence their galaxies by affecting star formation. 

For the investigation, astrophysicists Catherine Grier and Robert Wheatley analyzed over eight years of data from the quasar SBS 1408+544, collected by the Sloan Digital Sky Survey’s Black Hole Mapper Reverberation Mapping Project

Intense light from quasars 

According to scientists, black holes reside at the centers of most galaxies. Quasars are supermassive black holes encircled by disks of matter being drawn in by a massive gravitational pull.

“The material in that disk is always falling into the black hole, and the friction of that pulling and pulling heats up the disk and makes it very, very hot and very, very bright,” explained Grier. 

“These quasars are really luminous, and because there’s a large range of temperatures from the interior to the far parts of the disk, their emission covers almost all of the electromagnetic spectrum.”

The intense light from quasars, which can be as old as the universe itself, allows them to be seen from billions of light years away. Their broad electromagnetic radiation range makes them valuable for studying the early universe.

Accelerating winds from black holes 

Focusing on the data from quasar SBS 1408+544, located billions of light years away in the constellation Boötes, the researchers observed gaseous carbon winds by detecting missing light absorbed by the gas.

With each observation, the absorption shifted further in the spectrum, indicating the gas’s increasing velocity.

“That shift tells us the gas is moving fast, and faster all the time,” said Wheatley. “The wind is accelerating because it’s being pushed by radiation that is blasted off of the accretion disk.”

Previous studies had suggested accelerating winds from black hole accretion disks, but lacked substantial observational data.

The new findings, based on approximately 130 observations over nearly a decade, provide solid evidence of the increasing velocity. These quasar winds are significant because they can impact the host galaxy’s evolution. 

Quasar winds may shape galaxies

“If they’re energetic enough, the winds may travel all the way out into the host galaxy, where they could have a significant impact,” said Wheatley. 

Depending on the conditions, the winds could either compress gas to hasten star formation or remove gas and prevent star formation.

“Supermassive black holes are big, but they’re really tiny compared to their galaxies,” noted Grier. “That doesn’t mean they can’t ‘talk’ to each other, and this is a way for one to talk to the other that we will have to account for when we model the effects of these kinds of black holes.”

Quasars and their galaxies

This study, published in The Astrophysical Journal, highlights the dynamic relationship between quasars and their galaxies, providing new insights into galaxy formation. 

Long-term observations and detailed data are crucial for understanding these complex processes.

“Broad absorption lines (BALs) in the spectra of quasars are thought to originate in winds that are launched from quasar accretion disks,” wrote the study authors. 

“Characterizing these BALs and their environments to constrain models for how they are produced, how they evolve, and how they affect their galaxies, is thus important for our understanding of galaxy evolution.”

More about black hole winds

Black hole wind refers to the powerful outflows of matter and energy driven by the intense gravitational forces and magnetic fields near a black hole

As matter from the surrounding accretion disk spirals into the black hole, some of it is heated to extreme temperatures and accelerated to high speeds. 

This process generates strong radiation and magnetic fields, which can expel streams of ionized gas and other particles away from the black hole at significant fractions of the speed of light. 

These outflows, or winds, can have substantial effects on their surroundings, influencing the dynamics of their host galaxies by regulating star formation and redistributing matter and energy. 

The winds are an important mechanism in the feedback processes that shape the evolution of galaxies and the growth of black holes themselves.

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