active galactic nuclei The bright, noisy nuclei of galaxies. Supermassive Black Holes Huge amounts of matter are accreting: the most stable and brightest objects in the sky. But it may be much brighter and more vibrant than astronomers believed, a new paper in the Monthly Notices of the Royal Astronomical Society argues. Based on observations of one of the most widely analyzed AGNs, NGC 5548, the team behind the study found that the region around the nucleus is much dustier than astronomers previously estimated, meaning the AGN may be ejecting dozens more. . times the energy than anyone expected.
what’s new – NGC 5548 was one of the first active galaxies observed by astronomers. 80 years ago Carl sv They were found to have wider and more intense emission lines than other galaxies that would appear identical to the naked eye. Astronomers use a variety of spectra to understand the energies produced by active galactic nuclei, but because they are so bright, you would expect them to far dwarf any dust that orbits them. It turns out that this is not the case. Said lead author C. Martin Gaskell in a press release: “The far-ultraviolet light from a typical active galactic nucleus is dimmed by a significant factor.” This causes a problem known to astronomers as reddening: Energies from these massive black holes are reflected off tiny dust grains at lower wavelengths, making the longer wavelengths, toward the redder end of the spectrum. , arrive here hundreds of millions of years later. . .
“When there are small particles along our line of sight, this makes objects behind them appear dimmer. We notice it at sunset on any clear day when the sun looks darkest,” explains Gaskell. In the same way that the Sun darkens and reddens as it settles in the west, the incredible energies released by the supermassive black hole at the heart of NGC 5548, a mass 65 million times more massive than the Sun, are obscured. and reddened by the huge cloud of dust gathering around them.
NGC 5548 has one of the best-studied supermassive black holes at its center. European Space Agency/Hubble and NASA. Acknowledgments: David D. Martin. Why That Matters – Historically, astronomers have focused on correcting for the redness of active galactic nuclei based on indicators from our own galaxy. But fortunately, our familiar Milky Way is not itself an active galaxy. The indicators the team focused on at NGC 5548 found that the dust-based dimming around its accretion disk was about fifteen times stronger than the process in our galaxy. Since most of the supermassive black hole’s energy is pumped out in the ultraviolet range, Gaskell says, this means that a typical active galactic nucleus is pumping out much more energy than usual methods would have astronomers expect. This discrepancy also matches that of the 2013 Active Space Telescope Galaxy Nuclei and Optical Return Mapping Project, or, painfully, AGNSTORM for short. AGNSTORM has measured a variety of AGNs in different spectra (their wavelengths are measured in angstroms) to try to understand the size of the accretion disk around these supermassive black holes.