Friday, August 12

Astronomers measure masses of more than 800 supermassive black holes | Digital Trends Spanish


The largest census of supermassive black holes in the nearby or local universe – those colossi that grow devouring everything in the active nuclei of galaxies and that have up to billions of times the mass of our Sun – has been revealed by the international scientific team of the project BASS Surveyafter more than 15 years of research including an outstanding participation of astronomers and astronomers from the Center for Astrophysics and Related Technologies (CATA), from Chile.

The research, which was published in the latest edition of the Astrophysical Journal, includes a series of scientific publications that used data from large telescopes in the north of our country, the United States, and NASA’s Swift Space Observatory, achieving an extensive accumulation of information that has made it possible to build a map of these active black holes and their intense emissions in the nearby universe.

Hundreds of hours of observation and analysis were required to carry out this task, revealing the masses of supermassive black holes in galactic centers with a level of detail that had been impossible to achieve until now. “The map is representative of active black holes in the local universe. It has more than 800 supermassive black holes in a distance range of more than 5 billion light years. The main novelty is that it was possible to estimate the most important physical properties for a large sample of supermassive black holes, such as their masses and accretion or growth rates”, explains Claudio Ricci, an astronomer from the Diego Portales University, a CATA researcher and one of the principal scientists of the BASS Survey project.

According to the research, when a substantial amount of dust and gas surrounds a supermassive black hole, it can form an accretion disk that emits large amounts of light across the electromagnetic spectrum, peaking in the optical and ultraviolet range, at
as it falls into the black hole.

Franz Bauer, CATA researcher and academic at the Institute of Astrophysics of the Catholic University, who also participated in the research, explains that this same dust and gas, however, can also block our view of the so-called central engine, or nuclei.
“active” galaxies (AGN), making it difficult to observe these giants with traditional instruments and techniques.

“This implies that although many supermassive black holes are actively accreting material and growing, we don’t easily see them at visual wavelengths and don’t take them into account,” he says. This barrier was overcome thanks to the instrument on board the Swift Observatory known as BAT (Burst Alert Telescope), capable of detecting high-energy x-rays also known as “hard X-rays”, associated with high-energy emissions from supermassive black holes.

Goethe University

“It’s similar to the process of taking an X-ray, as this instrument looked at a similar frequency. In this case, it would be like a cosmic X-ray to observe the nuclei of galaxies where these growing black holes are”, explains Ezequiel Treister, Deputy Director of CATA and an astronomer at the Catholic University of Chile, who was also part of the research.

Claudio Ricci points out that at those energy levels, the radiation interacts very little with the material in its path, allowing “also to detect some of the darkest black holes. This has made it possible for us to have an almost complete sample of black holes in the accretion phase (growth) in the centers of nearby galaxies”, details the researcher. The speed at which these black holes grow varies greatly – adds the astronomer – from the equivalent of the mass of Uranus per year, to those that “swallow” the equivalent of 30 Jupiter planets in a similar period”.

In addition to the Swift Observatory and BAT, more than 10 ground-based optical and infrared telescopes were used in our country (Chile) and other parts of the world. Ezequiel Treister highlights that “it is a collaborative work, which required the combined work of telescopes in the southern and northern hemispheres, in order to study the active nuclei of galaxies distributed throughout the sky. The mass measurements were possible thanks to many observations made from the Chilean desert”.

One of the results published in this study, led from Chile, was obtained using infrared spectroscopy to measure the mass of more than 300 highly obscured supermassive black holes. “Thanks to these data we have been able to measure the mass of black holes, detecting the movement of clouds rotating at high speed in their surroundings, including completely obscured systems where this was not possible. This shows the importance of combining multiple observatories” says Dr. Federica Ricci, who was a FONDECYT postdoctoral researcher at the Catholic University and who is currently continuing her research career in Italy.

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