The study of space provides the clearest understanding yet of the life cycle of supermassive black holes

The study of space provides the clearest understanding yet of the life cycle of supermassive black holes

The circular cake-shaped ring that surrounds several supermassive black holes tells researchers how fast a space object is fed, and could change how the black hole is seen from Earth. Credit: ESA/NASA, The AVO Project and Paolo Padovani

According to a study by Dartmouth researchers, black holes with varying light signatures, but thought to be the same things viewed from different angles, are actually in different stages of the life cycle.

The search for black holes is known asActive Galactic Nuclei,” or AGNs, emphatically demonstrates the need to revise the “widely used standardized model of AGN” that characterizes supermassive black holes As they all have the same characteristics.

The study published in The Astrophysical Journal Supplement Seriesprovides answers to a disturbing space puzzle and should allow researchers to create more accurate models about the evolution of the universe and how black holes evolve.

“These things have puzzled researchers for more than half a century,” said Tonima Tasnim Inanna, a postdoctoral researcher at Dartmouth and lead author of the paper. “Over time, we have made many assumptions about the physics of these objects. Now we know that the properties of occult black holes are very different from those of strongly hidden active galactic nuclei.”

Supermassive black holes are believed to be at the center of nearly all large galaxies, including the Milky Way. Objects devour galactic gases, dust, and stars, and can become heavier than small galaxies.

For decades, researchers have been interested in the optical signatures of active galactic nuclei, a type of supermassive black hole that is “accumulating,” or in a rapidly growing phase.

Beginning in the late 1980s, astronomers realized that light signals from space ranging from radio wavelengths to X-rays could be attributed to AGNs. It was assumed that the objects usually had a circular-shaped ring – or “hoop” – of gas and dust around them. The different brightness and colors associated with objects were thought to result from the angle from which they are observed and the amount of torus blocking the view.

From here, the unified theory of the active galactic nucleus became the dominant concept. The theory instructs that if a black hole is viewed through its throat, it should appear faint. If viewed from the bottom or top of the ring, it should appear bright. According to the current study, previous research relied heavily on data from less obscure objects and skewed research results.

The new study focuses on how quickly black holes feed on space matter, or their accretion rates. The research found that the accretion rate does not depend on the mass of the black hole, it varies greatly depending on how much it is obscured by the gas and dust ring.

“This provides support for the idea that not all the toroidal structures around black holes are the same,” said Ryan Hickox, a professor of physics and astronomy and one of the study’s authors. “There is a connection between the structure and how it grows.”

The result shows that the amount of dust and gas surrounding the AGN is directly related to the amount of nutrition, confirming that there are differences beyond the trend between different groups of AGN. When a black hole accumulates at a high rate, the energy expels dust and gas. As a result, they are more likely to be unobstructed and appear brighter. Conversely, the less active AGNs are surrounded by a denser ring and appear fainter.

“In the past, it was not certain how the group of obscured AGNs differed from their more easily observable and unobstructed counterparts,” Ananna said. “This new research conclusively shows a fundamental difference between the two groups that goes beyond viewing angle.”

The study stems from a decade-long analysis of nearby active galactic nuclei detected by Swift-BAT, NASA’s high-energy X-ray telescope. The telescope allows researchers to examine the local universe to discover unobscured and unobscured AGNs.

The research is the result of an international scientific collaboration – the BAT AGN Spectroscopy Survey (BASS) – that has worked over a decade to collect and analyze optical/infrared spectroscopy of AGN monitored by Swift BAT.

“We’ve never had such a large sample of X-rays detected before that obscured a locally active galactic nucleus,” Annan said. “This is a huge benefit for high-energy X-ray telescopes.”

The paper builds on previous research from the research team that analyzed AGNs. For the study, Ananna developed a computational technique to assess the effect of dimming on the observed properties of black holes, and analyzed data collected by the broader research team using this technique.

According to the research paper, by knowing the mass of a black hole and how fast it feeds, researchers can determine when most supermassive black holes underwent most of their growth, thus providing valuable information about the evolution of black holes and the universe.

“One of the biggest questions in our field is where is supermass located black holes Hickox said. “This research presents an important piece that can help us answer this question and I expect it to become a reference for this research discipline.”

future Research It could include focusing on wavelengths that allow the team to search outside the local universe. In the near term, the team would like to understand what motivates AGNs to enter high-accumulation mode, and how long it takes for AGNs to quickly go from highly obscured to unobscured.


Astronomers survey less dense black holes at the center of galaxies in the local universe


more information:
Tunima Tasnim Inanna et al., Bass. XXX. DR2 Eddington ratio distribution functions, black hole masses and X-ray illumination, The Astrophysical Journal Supplement Series (2022). DOI: 10.3847 / 1538-4365 / ac5b64

Introduction of
Dartmouth College


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