Penn State researchers recently characterized more than a hundred blazars (distant, dynamic galaxies at their centers where a supermassive black hole drives powerful jets) from a catalog of previously unclassified high-energy cosmic emissions. The recently recognized blazars, which pale in comparison to most of their counterparts, have given scientists a chance to test a controversial theory about blazar emission. This new information contributes to our understanding of the expansion of black holes and even influences our theories of general relativity and high-energy particle physics.

Supermassive black holes can be millions or billions of times the mass of our Sun. In some cases, matter outside the black hole’s event horizon travels in a jet, reaching nearly the speed of light and sending emissions throughout the universe. When the jet is aimed directly at Earth, the system is often referred to as a blazar.

“Because Blazar’s jet is pointed directly at us, we can see them much further away than other black hole systems, just as a flashlight looks brightest when you look directly at it,” said Stephen Kirby, a graduate student in astronomy and astrophysics. University of Pennsylvania and first author of the article. “Studying blazars is fascinating because their properties allow us to answer questions about supermassive black holes in the universe. In this study, we used relatively new techniques to characterize 106 faint blazars and test the predictions of a controversial theory called the ‘blazar array’.

Blazars emit light across the entire electromagnetic spectrum, from low-energy waves such as radio, infrared and visible light to higher-energy waves such as X-rays and gamma rays. When astronomers examine observations of these emissions, they typically see two broad peaks, one in gamma rays and the other in low-energy waves. The wavelengths and intensity of these peaks vary from blazar to blazar and over time. The general theory of blazars, defined by the “blazar sequence”, predicts that the lower energy peak for brighter blazars will be, on average, redder – lower energy – than the peak for paler blazars, with a lower energy peak for paler blazars. be bluer – higher energy.

“Some of the most exciting and extreme blazars are detected by detecting gamma-ray emissions, but we often cannot classify or understand these objects without further multi-wavelength observations,” said Abe Falcone, research professor and high-tech leader in astronomy and astrophysics. -resolution astrophysics group, energy in the state of Pennsylvania. “With our current telescopes, it is actually very difficult to detect and classify low-energy peak blazars – the red ones – that are also dim, whereas it is much easier to find these blazars when their peaks are at higher energy or when they are bright. We are minimizing selection bias by examining the low luminosities of peak blazars more deeply and investigating the blazar array.”

Along with Amanpreet Kaur, a research associate in astronomy and astrophysics at the University of Pennsylvania at the time of the study, the researchers identified potential blazars from a catalog of gamma-ray sources previously detected by the Large Fermi Telescope. had not yet been discovered. combined with lower energy emissions that may have come from the same source. Next, the researchers determined for each of the blazars the corresponding emission and infrared in X-ray, ultraviolet and optical radiation detected by the Neil Gehrels Swift Observatory, whose center of operations is in Pennsylvania. and radio emission from archive data. . Cross-referencing the information eventually allowed the researchers to characterize the spectrum of 106 new dim blazars.

“Observations with the Swift telescope have allowed us to pinpoint the positions of these blazars much more precisely than we could with Fermi data alone,” Kerby said. Said. “Combining all this emission data with two new technical approaches helped us determine where in the electromagnetic spectrum the low energy peak occurred for each of the blazars, which could, for example, provide information about the strength of the magnetic jet of the jet field, the speed of movement of charged particles, and other information”.

To determine where this peak occurred for dim blazars, the researchers used machine learning and direct physical fit approaches, which Kirby said each had advantages and disadvantages. The machine learning approach filters out emissions that could actually be noise, such as dust in a galaxy or light from other stars. The direct physical docking approach does not filter out noise and is much more difficult to use, but provides more detailed specifications of the blazar jet.

“For both approaches, the emission of our dim blazar sample typically peaks in higher-energy blue light, but the fitting approach produces less extremes,” Kerby said. “This is consistent with the blazar array and expands what we know about this pattern. However, there are still thousands of unrelated Fermi sources for which we have not found an X-ray counterpart, and we can also assume that many of these sources are blazars that are too faint for us to detect in X-rays. We can use the lessons we’ve learned here about the shape of the blazar to further test the blazar array to make predictions about blazars that are still too faint for us to detect.”

A catalog of new blazars is available to other astronomers for further study.

“It’s important to always work to expand our datasets to include even weaker sources, as this makes our theories more complete and less prone to error due to unexpected biases,” Kerby said. “I’m excited about new telescopes to study even fainter blazars in the future.”

According to the researchers, studying supermassive black holes also provides a unique way to understand physical theories in the universe.

“Supermassive black holes and their surroundings are space labs with far more energy than anything we can generate in particle accelerators on Earth,” Falcone said. Said. “They allow us to study relativity, better understand how particles behave at high energies, examine potential sources of cosmic rays reaching Earth, and study the evolution and formation of supermassive black holes and their jets.” Source