Many large galaxies convey a brilliant fundamental portion called an active galactic nucleus (AGN), powered yesteryear thing spiraling into a supermassive dark hole. Gas clouds inwards an surface area to a greater extent than or less the AGN known every bit the "broad-line region" emit lite at characteristic wavelengths, but the complexity too variability of these emissions has been a longstanding puzzle for astrophysicists.
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| An artist's impression of what an active galactic nucleus mightiness await similar unopen up. The accretion disk produces the brilliant lite inwards the center. The broad-line portion is exactly higher upwards the accretion disk too lost inwards the glare. |
Dust clouds are beingness driven upward yesteryear the intense radiations [Credit: Peter Z. Harrington] Influenza A virus subtype H5N1 novel analysis yesteryear researchers at UC Santa Cruz, published inwards Monthly Notices of the Royal Astronomical Society, explains these too other puzzling features of active galactic nuclei every bit the resultant of small-scale clouds of dust that tin partially obscure the innermost regions of AGNs.
"We've shown that a lot of mysterious properties of active galactic nuclei tin endure explained yesteryear these small-scale dusty clouds causing changes inwards what nosotros see," said showtime writer Martin Gaskell, a question associate inwards astronomy too astrophysics at UC Santa Cruz.
The findings convey of import implications because researchers piece of occupation the optical emissions from the broad-line portion to brand inferences almost the demeanour of the gases inwards the inner regions to a greater extent than or less a supermassive dark hole.
"The emission from this gas is ane of the best sources of information almost the majority of a dark hole too how it is growing. However, the nature of this gas is poorly understood," Gaskell said.
Coauthor Peter Harrington, a UCSC graduate pupil who began piece of occupation on the projection every bit an undergraduate, explained that gas spiraling toward a galaxy's fundamental dark hole forms a apartment accretion disk, too the superheated gas inwards the accretion disk emits intense thermal radiation. Some of that lite is "reprocessed" (absorbed too re-emitted) yesteryear hydrogen too other gases swirling higher upwards too below the accretion disk inwards the broad-line region. Above too beyond this is a portion of dust.
"Once the dust crosses a for sure threshold it is subjected to the potent radiations from the accretion disk," said Harrington. "This radiations is thus intense that it blows the dust away from the disk, resulting inwards a clumpy natural springtime of dust clouds starting at the outer border of the broad-line region."
The resultant of the dust clouds on the lite emitted is to brand the lite coming from behind them await fainter too redder, exactly every bit Earth's atmosphere makes the Sun await fainter too redder at sunset. In their paper, Gaskell too Harrington introduce several lines of observational testify supporting the existence of such dust clouds inwards the inner regions of active galactic nuclei. They developed a estimator code to model the effects of dust clouds on observations of the broad-line region.
"We've written the code thus nosotros tin conform parameters similar the distribution of gas inwards the broad-line region, how fast it's moving, too the orientation of the system, too thus nosotros tin innovate dust clouds too meet how they impact the emission-line profiles," Harrington said.
The results present that yesteryear including dust clouds inwards their model, it tin replicate many features of emission from the broad-line portion that convey long puzzled astrophysicists. Rather than the gas having a changing, asymmetrical distribution that is difficult to explain, the gas is only inwards a uniform, symmetric, turbulent disk to a greater extent than or less the dark hole. The apparent asymmetries too changes are due to dust clouds passing inwards forepart of the broad-line portion too making the regions behind them await fainter too redder.
"We recollect it is a much to a greater extent than natural explanation of the asymmetries too changes than other to a greater extent than exotic theories, such every bit binary dark holes, that convey been invoked to explicate them," Gaskell said. "Our explanation lets us retain the simplicity of the criterion AGN model of thing spiraling onto a unmarried dark hole."
Author: Tim Stephens | Source: University of California - Santa Cruz [June 14, 2018]
Sumber http://archaeologynewsnetwork.blogspot.com
"We've shown that a lot of mysterious properties of active galactic nuclei tin endure explained yesteryear these small-scale dusty clouds causing changes inwards what nosotros see," said showtime writer Martin Gaskell, a question associate inwards astronomy too astrophysics at UC Santa Cruz.
The findings convey of import implications because researchers piece of occupation the optical emissions from the broad-line portion to brand inferences almost the demeanour of the gases inwards the inner regions to a greater extent than or less a supermassive dark hole.
"The emission from this gas is ane of the best sources of information almost the majority of a dark hole too how it is growing. However, the nature of this gas is poorly understood," Gaskell said.
Coauthor Peter Harrington, a UCSC graduate pupil who began piece of occupation on the projection every bit an undergraduate, explained that gas spiraling toward a galaxy's fundamental dark hole forms a apartment accretion disk, too the superheated gas inwards the accretion disk emits intense thermal radiation. Some of that lite is "reprocessed" (absorbed too re-emitted) yesteryear hydrogen too other gases swirling higher upwards too below the accretion disk inwards the broad-line region. Above too beyond this is a portion of dust.
"Once the dust crosses a for sure threshold it is subjected to the potent radiations from the accretion disk," said Harrington. "This radiations is thus intense that it blows the dust away from the disk, resulting inwards a clumpy natural springtime of dust clouds starting at the outer border of the broad-line region."
The resultant of the dust clouds on the lite emitted is to brand the lite coming from behind them await fainter too redder, exactly every bit Earth's atmosphere makes the Sun await fainter too redder at sunset. In their paper, Gaskell too Harrington introduce several lines of observational testify supporting the existence of such dust clouds inwards the inner regions of active galactic nuclei. They developed a estimator code to model the effects of dust clouds on observations of the broad-line region.
"We've written the code thus nosotros tin conform parameters similar the distribution of gas inwards the broad-line region, how fast it's moving, too the orientation of the system, too thus nosotros tin innovate dust clouds too meet how they impact the emission-line profiles," Harrington said.
The results present that yesteryear including dust clouds inwards their model, it tin replicate many features of emission from the broad-line portion that convey long puzzled astrophysicists. Rather than the gas having a changing, asymmetrical distribution that is difficult to explain, the gas is only inwards a uniform, symmetric, turbulent disk to a greater extent than or less the dark hole. The apparent asymmetries too changes are due to dust clouds passing inwards forepart of the broad-line portion too making the regions behind them await fainter too redder.
"We recollect it is a much to a greater extent than natural explanation of the asymmetries too changes than other to a greater extent than exotic theories, such every bit binary dark holes, that convey been invoked to explicate them," Gaskell said. "Our explanation lets us retain the simplicity of the criterion AGN model of thing spiraling onto a unmarried dark hole."
Author: Tim Stephens | Source: University of California - Santa Cruz [June 14, 2018]
Sumber http://archaeologynewsnetwork.blogspot.com
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