Hidden supermassive black holes brought to life by galaxies on a collision course

Astronomers have found that dust-obscured supermassive black holes are likely to grow larger and release enormous amounts of energy when inside galaxies that are expected to collide with a neighboring galaxy. The new work, led by researchers at Newcastle University, has been published in the journal Monthly Notices of the Royal Astronomical Society. Galaxies, including our own Milky Way, contain supermassive black holes at their centers. They have a mass equivalent to millions or even billions of times that of our sun. These black holes grow by “eating” the gas that falls on them. However, what drives the gas near black holes to make this happen is an ongoing mystery.

One possibility is that when galaxies are close enough to each other, they are likely to be gravitationally pulled towards each other and “merge” into a larger galaxy. In the final stages of its journey towards the black hole, the gas ignites and releases a large amount of energy. This energy is usually detected using visible light or X-rays. However, the astronomers conducting this study were only able to detect the growing black holes using infrared light. The team used data from many different telescopes, including the Hubble Space Telescope and the infrared Spitzer Space Telescope. Researchers have developed a new technique to determine the probability that two galaxies that are so close together will collide in the future. They applied this new method to hundreds of thousands of galaxies in the distant Universe (observing galaxies that formed 2 to 6 billion years after the Big Bang) in an effort to better understand so-called “cosmic noon,” a time when most than expected The occurrence of growth in the galaxy of the universe and the black hole.

Understanding how black holes grew during this time is key to modern galactic research, especially since it could give us insight into the supermassive black hole that resides within the Milky Way and how our galaxy has evolved over time. Being so far away, only a few of the midday cosmic galaxies meet the criteria for accurate measurements of their distances. This makes it very difficult to say with great precision if two galaxies are very close together. This study presents a new statistical method to overcome previous limitations of measuring the exact distances of galaxies and supermassive black holes at cosmic noon. It applies a statistical approach to determining the distances of galaxies using images at different wavelengths and eliminates the need for spectral distance measurements for individual galaxies. Data from the James Webb Space Telescope over the next few years is expected to revolutionize infrared studies and reveal more secrets about how these dusty black holes grow. “Our new approach looks at hundreds of thousands of distant galaxies with a statistical approach and asks how likely it is that two galaxies are very close together and most likely on a collision course,” says Sean Dougherty, a graduate student at the University. of Newcastle and lead author of the article.

Chris Harrison, co-author of the study, says: “These supermassive black holes are very difficult to find because the X-ray light, which astronomers typically use to find these growing black holes, is blocked from being detected by our telescopes. But these black holes can be found.” It uses infrared radiation, which is produced by the surrounding hot dust.

source: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stad1300/7152624?login=false