Some Galaxies Look Brighter Due To Their Black Holes

Posted: Sep 29 2017, 8:42am CDT | by , in News | Latest Science News

 
Some Galaxies Look Brighter Due to their Black Holes
Credit: NASA/JPL-Caltech

Eating habits of black holes determines the brightness of the galaxies

Astronomers have taken a critical step towards understanding why some galaxies in the universe appear brighter than the others.

For years, astronomers have been able to observe galaxies beyond our own galaxy with the help of powerful telescopes and their observations suggest that two of the most common types of active galaxies, known as Type I and Type II galaxies, look different when seen from Earth.

Despite the fact that both types of galaxies harbor supermassive black holes at their center – the most powerful gravitational spots in the entire universe that swallow nearby matter and brighten the surroundings by releasing enormous amount of energy – Type I galaxies shine more brightly.

Existing theory says that both type I and Type II galaxies are fundamentally the same. They look different solely because the galaxies point toward Earth at different angles. However, researchers have found that both types are very different from each other both in structure and energetic profile. The thing that separates the type I from the type II is the rate at which their central black holes consume matter and emit light. New findings challenge the basic assumption of the popular theory called the unified model and demand an adjustment to account for the new surprising observations.

"The unified model has been the prevailing wisdom for years. However, this idea does not fully explain the differences we observe in galaxies' spectral fingerprints, and many have searched for an additional parameter that fills in the gaps," said co-author Richard Mushotzky, a professor of astronomy at University of Maryland. "Our new analysis of X-ray data from NASA's Swift Burst Alert Telescope suggests that Type I galaxies are much more efficient at emitting energy.”

In the latest effort, researchers have re-examined data from 836 active galaxies detected by NASA's Swift Burst Alert Telescope that strongly emit high-energy X-rays and measure the mass and growth rate of supermassive black holes at the center of these galaxies. To complement the observations taken by the Swift satellite, researchers also looked at the data from 12 different ground-based telescopes around the world.

Researchers found that central black holes in Type I galaxies consume matter and emit energy much faster compared with the black holes at the center of Type II galaxies. Their X-ray spectra appears different, regardless of which way the galaxy faces Earth.

“Our results suggest this has a lot to do with the amount of dust that sits close to the central black hole," said Mushotzky. "Type II galaxies have a lot more dust close to the black hole, and this dust pushes against the gas as it enters the black hole."

Black holes are on the most intriguing objects in the universe and researchers have repeatedly observed the result of black hole interactions with the surrounding matter in order to understand the nature of black holes. Latest findings could help expand their understanding of the galaxies and the black holes sitting in their hearts.

“Now, because our results suggest that the two types of galaxies are indeed fundamentally different, it is likely that a lot of researchers will re-evaluate their data and take another look at Type I galaxies," said Mushotzky. "By putting us on a path to better understand the differences between the galaxies that host Type I and Type II active nuclei, this work will help us better understand how supermassive black holes influence the evolution of their host galaxies."

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Hira Bashir covers daily affairs around the world.

 

 

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