Using observations from NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), a Boeing 747SP jetliner modified to carry a 100-inch telescope, astronomers have found that the dust surrounding active supermassive black holes is much more compact than previously thought.
Artist illustration of the thick ring of dust that can obscure the energetic processes that occur near the supermassive black hole of an active galactic nucleus. Image credit: NASA / SOFIA / Lynette Cook.
Most, if not all, large galaxies contain a supermassive black hole at their centers.
Many of these black holes are relatively quiet and inactive, like the one at the center of our Milky Way Galaxy.
However, some supermassive black holes are currently consuming significant amounts of material that are being drawn into them, resulting in the emission of huge amounts of energy. These active black holes are called active galactic nuclei (AGN).
Previous studies have suggested that all AGNs have essentially the same structure.
Models indicate that AGNs have a donut-shaped dust structure, known as a torus, surrounding the supermassive black hole.
Using SOFIA’s FORCAST instrument, Lindsay Fuller of the University of Texas, San Antonio, and co-authors observed the infrared emissions around 11 supermassive black holes in AGNs located at distances of 100 million light-years and more, and determined the size, opacity, and distribution of dust in each torus.
According to the team, the tori are 30% smaller than predicted and that the peak infrared emission is at even longer infrared wavelengths than previously estimated.
The implication is that the dust obscuring the central black hole is more compact that previously thought.
They also indicate that AGNs radiate most of their energy at wavelengths that are not observable from the ground because the energy is absorbed by water vapor in Earth’s atmosphere.
“Using SOFIA, we were able to obtain the most spatially detailed observations possible at these wavelengths, allowing us to make new discoveries on the characterization of AGN dust tori,” Fuller said.
“Future observations are necessary to determine whether or not all of the observed emission originates with the tori, or if there is some other component adding to the total emission of AGNs.”
“Next, our goal will be to use SOFIA to observe a larger sample of AGNs, and at longer wavelengths,” said co-author Dr. Enrique Lopez-Rodriguez, Universities Space Research Association staff scientist at the SOFIA Science Center.
“That will allow us to put tighter constraints on the physical structure of the dusty environment surrounding AGNs.”
The findings were recently published in the Monthly Notices of the Royal Astronomical Society.
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L. Fuller et al. 2016. Investigating the dusty torus of Seyfert galaxies using SOFIA/FORCAST photometry. Mon Not R Astron Soc 462 (3): 2618-2630; doi: 10.1093/mnras/stw1780
This article is based on text provided by the National Aeronautics and Space Administration.
