More than a hundred belzars — distant, active galaxies with a central supermassive black hole driving powerful jets — have been newly described by Penn State researchers from a catalog of previously unclassified high-energy cosmic emissions. The new blazars, which are dim relative to more typical blazars, have allowed researchers to test a controversial theory of blazar emission, elucidating our understanding of black hole growth and even theories of general relativity and high-energy particle physics.
A paper describing blazars and the theory has been accepted for publication in Astrophysical Journaland the accepted, peer-reviewed version appears online on the prepress server arXiv.
enormous black holes The mass of our sun can be in millions or billions of times. In some cases, matter is propelled out of the black hole’s event horizon in a jet, accelerating nearly to the speed of light and sending emissions across the universe. When the aircraft happens to be pointed directly at the ground, the system is usually called Blazar.
“Because the Blazar jet is pointed directly at us, we can see it from a much greater distance than other black hole systems, similar to how the flashlight appears brighter when you look directly at it,” said Stephen Kirby, a graduate student. in astronomy and astrophysics at Penn State and first author of the paper.
Blazars are exciting to study because their properties allow us to answer questions about them supermassive black holes all over the universe. In this study, we used relatively new methods to describe 106 dark blazars and test the predictions of a controversial theory called the ‘Blazar Sequence’.
Blazars emit light across the entire electromagnetic spectrum, from lower energy wavelengths such as radio, infrared, and visible light, through to higher energy wavelengths such as x-rays and gamma rays. When astronomers study observations of these emissions, they usually see two broad peaks, one in gamma rays and one in lower-energy wavelengths.
The wavelengths and intensities of these peaks vary from blazar to blazar and over time. A comprehensive theory about blazars identified by the “blazars sequence” predicts that the low-energy peak of brighter blazars will be, on average, redder – lower energy – than that of dimmer blazars, while the lower-energy peak of dim blazars will be bluer – energy higher.
said Abe Falcone, research professor of astronomy and astrophysics and team leader of the High Energy Astrophysics Group at Penn State.
“With telescopes that are currently in operation, it is very difficult to detect and classify low-energy peak-red-faint blazars as well, while it is much easier to find these blazars when their peaks are at higher energies or when they are bright. So, with this research, We reduce selection bias and explore blazar sequences by delving deeper into the low brightness of both low-energy and high-energy blazars.”
The researchers, along with Amanpreet Kaur — a research associate professor of astronomy and astrophysics at Penn State at the time of the research —previously identified potential plazas From the catalog of gamma-ray sources detected by the Large Fermi Telescope, many of which have not yet been paired with lower-energy emissions that may have come from the same source.
For each of the blazars, the researchers then located these isotope emissions in X-ray, ultraviolet, and optical light — detected by the Neil Gehrels Swift Observatory, whose mission operations center is in Pennsylvania — and in infrared and radio emissions from archival data. Cross-referencing the information finally allowed the researchers to characterize the spectra of 106 new dim blazars.
“Swift’s observations have allowed us to pinpoint the locations of these blazars with much greater precision than the Fermi data alone,” Kirby said. “Collecting all this emission data, along with two new technical approaches, has helped us pinpoint where in the electromagnetic spectrum for each of the blazars the low-energy peak occurs, which, for example, can provide information about the strength of the aircraft’s magnetism and how fast the particles are moving. charged and other information.
To determine where this peak of fainting trees occurred, the researchers used machine learning methods and direct physical synthesis, each of which, according to Kirby, has advantages and disadvantages. the machine learning The approach method filters out emissions that might actually be noise, such as dust in a galaxy or light from other stars. The direct physics compositing method does not filter out noise and is more difficult to use but provides more detailed characteristics of the Blazar plane.
“For both methods, our sample’s emissions from faint blazars generally peak in higher-energy blue light, although the fitting method yields less extreme values,” Kirby said.
This is consistent with the blazar sequence and extends to what we know about this pattern. However, there are still a thousand non-Fermi sources for which we have not found an X-ray counterpart, and it is a fairly safe assumption that many of these sources are also very faint blazars in the rays. “We can use the lessons we learned here about the shape of these blazar spectra to make predictions about blazars that are still too dim for us to detect, which will test the blazar sequence further.”
The catalog of new blazars is available for other astronomers to study in detail.
“It’s always important to work on expanding our datasets to reach dull and dim sources, because it makes our theories more complete and less prone to failure from unexpected biases,” Kirby said. “I’m excited about new telescopes to explore even the faintest Blazars In the future.”
According to the researchers, the study of supermassive black holes also provides a unique way to understand the physical theories of the universe.
“Supermassive black holes, and their surroundings, are cosmic laboratories far more energetic than anything we can produce in particle accelerators on Earth,” Falcon said. “They provide us with opportunities to study theories of relativity, to better understand how particles behave at high energies, to study possible sources of cosmic rays that arrive here on Earth, and to study the evolution and formation of supermassive black holes and their jets.”
Stephen Kirby et al., Blazar sequence testing using spectra of recently discovered faint blazars from the Fermi Unassociated Catalog, arXiv (2023). DOI: 10.48550/arxiv.2305.02087
Penn State University
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