University of California, Santa Cruz | 2018 Jun 14
Mysterious features seen in light emitted from active galactic nuclei may be due to partial obscuration by dust clouds, according to new study
Many large galaxies have a bright central region called an active galactic nucleus (AGN), powered by matter spiraling into a supermassive black hole. Gas clouds in an area around the AGN known as the "broad-line region" emit light at characteristic wavelengths, but the complexity and variability of these emissions has been a longstanding puzzle for astrophysicists.
- An artist’s impression of what an active galactic nucleus might look like close up. The accretion disk produces the brilliant light in the center. The broad-line region is just above the accretion disk and lost in the glare. Dust clouds are being driven upward by the intense radiation. (Credit: Peter Z. Harrington)
A new analysis by researchers at UC Santa Cruz, published June 14 in Monthly Notices of the Royal Astronomical Society, explains these and other puzzling features of active galactic nuclei as the result of small clouds of dust that can partially obscure the innermost regions of AGNs.
"We've shown that a lot of mysterious properties of active galactic nuclei can be explained by these small dusty clouds causing changes in what we see," said first author Martin Gaskell, a research associate in astronomy and astrophysics at UC Santa Cruz.
The findings have important implications because researchers use the optical emissions from the broad-line region to make inferences about the behavior of the gases in the inner regions around a supermassive black hole. ...
Partial Dust Obscuration in Active Galactic Nuclei as a Cause of Broad-Line Profile
and Lag Variability, and Apparent Accretion Disc Inhomogeneities - C. Martin Gaskell, Peter Z. Harrington
- Monthly Notices of the RAS 478(2):1660 (Aug 2018) DOI: 10.1093/mnras/sty848
arXiv.org > astro-ph > arXiv:1704.06455 > 21 Apr 2017 (v1), 29 Mar 2018 (v2)