Astronomie - The Recipe for Powerful Quasar Jets



    • Scientists are identifying the reasons why some black holes produce powerful beams, or jets, and others do not.

    • A new study of over 700 quasars (rapidly growing supermassive black holes) has revealed a possible answer.

    • Regions of diffuse hot gas threaded with powerful magnetic fields may dictate whether or not a supermassive black hole generates a jet.

  • This study combined data from NASA's Chandra X-ray Observatory, ESA's XMM-Newton, NSF's Very Large Array, and the Sloan Digital Sky Survey.


Scientists have studied more than 700 quasars — rapidly growing supermassive black holes — to isolate the factors that determine why some of these black holes launch jets and others do not, as reported in our latest press release. A new study using NASA's Chandra X-ray Observatory and other telescopes reveals the key role that regions of diffuse hot gas threaded with powerful magnetic fields — called a black hole "corona" — play in dictating whether the system creates a jet.

This artist's illustration depicts a supermassive black hole, and its corona (blue) threaded by magnetic fields (white). The corona lies above a much denser disk of material (red and yellow), swirling around and falling towards the black hole. Jets (white) of material are blasting away from the black hole and corona in opposite directions.

Supermassive black hole jets can inject huge amounts of energy into their surroundings and strongly influence the evolution of their environments. Previously, scientists realized that a supermassive black hole needs to be spinning rapidly to drive strong jets — but not all rapidly spinning black holes have jets.

The potential difference-maker appears to a black hole corona. Previous studies had shown that quasars without jets show a characteristic link between the strength of their X-ray and ultraviolet emission. This correlation is explained by ultraviolet light from the disk of the black hole striking particles in the corona. The resulting energy boost converts the ultraviolet light to X-rays.

In the new study the team chose to investigate the behavior of quasars that do have jets. They found a correlation between how bright the different quasars are in X-rays and ultraviolet light that is remarkably similar to that found for quasars without jets. They concluded that the X-ray emission in the jet-powering quasars is also produced by a black hole corona.

Previously, astronomers thought that X-ray emission from quasars with jets comes from the base of the jets because quasars with jets tend to be brighter in X-rays than those without. The new study confirms this difference in brightness, but concludes that the extra X-ray emission is from brighter black hole coronas than those of quasars with weaker or non-existent jets.

The team's sample consists of 729 quasars with jets. Chandra, ESA's XMM-Newton, and Germany's ROentgen SATellite (ROSAT) were used for 212, 278, and 239 quasars respectively. The size and quality of the team's sample explain why they were able to uncover the cause of the X-ray emission. The study also used data from the NSF's Karl G. Jansky Very Large Array and the Sloan Digital Sky Survey (SDSS) optical telescope.

Additional graphics show images of four quasars from the team's sample, with X-rays from Chandra in blue and radio waves from the VLA in red. The X-rays are mainly from the black hole's corona and the radio waves show the jets. The full names of the quasars and their distances from Earth are SDSS J122539.55+245836.3 (3.1 billion light years), SDSS J151443.07+365050.4 (4.1 billion light years), SDSS J083906.52+575417.0 (9.5 billion light years) and SDSS J091528.77+441632.8 (9.4 billion light years).


Credit: X-ray: NASA/CXO/Penn State Univ./S.F. Zhu et al.; Radio: NRAO/VLA/Penn State Univ./S.F. Zhu et al.

These results were published in the Monthly Notices of the Royal Astronomical Society on June 20th, 2020. The paper is also available online. The authors of the paper are Shifu Zhu and Niel Brandt (Penn State University in University Park), B. Luo (Nanjing University, China), Jianfeng Wu (Xiamen University, China), Y.Q. Xue (University of Science and Technology of China, Hefei), and G. Yang (Texas A&M University in College Station).

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge and Burlington, Massachusetts.

Quelle: Chandra X-ray Center, Operated for NASA


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