Researchers at the University of California, Santa Cruz (UCSC), believe clouds of dust, rather than twin dark holes, tin give the axe explicate the features constitute inwards active galactic nuclei (AGNs). The squad issue their results inwards a newspaper inwards Monthly Notices of the Royal Astronomical Society.
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| An artist’s impression of what an active galactic nucleus powerfulness facial expression similar at unopen quarters. The accretion disk produces the brilliant calorie-free inwards the centre. The broad-line percentage is exactly inwards a higher house the accretion disk in addition to lost inwards the glare. Dust clouds are existence driven upwards past times the intense radiations [Credit: Peter Z. Harrington] |
The emission from this gas is 1 of the best sources of information most the majority of the fundamental dark hole in addition to how it is growing. The nature of this gas is soundless poorly understood; inwards detail at that topographic point is less emission than expected from gas moving at surely velocities. The breakdown of unproblematic models has led some astrophysicists to intend that many AGNs powerfulness accept non 1 but 2 dark holes inwards them.
The novel analysis is led past times Martin Gaskell, a query associate inwards astronomy in addition to astrophysics at UCSC. Rather than invoking 2 dark holes, it explains much of the apparent complexity in addition to variability of the emissions from the broad-line percentage every bit the results of pocket-sized clouds of dust that tin give the axe partially obscure the innermost regions of AGNs.
Gaskell comments: "We've shown that a lot of mysterious properties of active galactic nuclei tin give the axe travel explained past times these pocket-sized dusty clouds causing changes inwards what nosotros see."
Co-author Peter Harrington, a UCSC graduate pupil who began run on the projection every bit an undergraduate, explained that gas spiralling towards a galaxy's fundamental dark hole forms a apartment "accretion disk", in addition to the superheated gas inwards the accretion disk emits intense thermal radiation. Some of that calorie-free is "reprocessed" (absorbed in addition to re-emitted) past times hydrogen in addition to other gases swirling inwards a higher house the accretion disk inwards the broad-line region. Above in addition to beyond this is a percentage of dust.
"Once the dust crosses a surely threshold it is subjected to the potent radiations from the accretion disk", said Harrington. The authors believe this radiations is in addition to thence intense that it blows the dust away from the disk, resulting inwards a clumpy fountain of dust clouds starting at the outer border of the broad-line region.
The resultant of the dust clouds on the calorie-free emitted is to brand the calorie-free coming from behind them facial expression fainter in addition to redder, exactly every bit the earth's atmosphere makes the Sun facial expression fainter in addition to redder at sunset. Gaskell in addition to Harrington developed a estimator code to model the effects of these dust clouds on observations of the broad-line region.
The 2 scientists also demonstrate that past times including dust clouds inwards their model, it tin give the axe replicate many features of emission from the broad-line percentage that accept long puzzled astrophysicists. Rather than the gas having a changing, asymmetrical distribution that is difficult to explain, the gas is exactly inwards a uniform, symmetric, turbulent disk approximately the dark hole. The apparent asymmetries in addition to changes are due to dust clouds passing inwards forepart of the broad-line percentage in addition to making the regions behind them facial expression fainter in addition to redder.
"We intend it is a much to a greater extent than natural explanation of the asymmetries in addition to changes than other to a greater extent than exotic theories, such every bit binary dark holes, that accept been invoked to explicate them," Gaskell said. "Our explanation lets us retain the simplicity of the criterion AGN model of affair spiralling onto a unmarried dark hole."
Source: Royal Astronomical Society [September 28, 2018]
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