A new study reveals that there are supermassive black holes at the centers of galaxies, known as quasars, that can sometimes be hidden behind dense clouds of gas and dust in the galaxies they are hosted in.
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This challenges the prevailing idea that quasars are only obscured by doughnut-shaped rings of dust around a black hole. Quasars are incredibly luminous objects powered by black holes that devour surrounding material. Their powerful radiation can be blocked by dense doughnut-shaped clouds surrounding them.
Astronomers have always assumed that this light-blocking material exists only in the immediate vicinity of a quasar. Now, a research team led by scientists at Durham University has discovered evidence that shows that in some quasars, the obscuration is due solely to the galaxy to which the quasar belongs.
Using the Atacama Large Millimeter Array (ALMA) in Chile, they observed a sample of quasars with intense star formation rates. They discovered that many of these quasars live in very compact galaxies, known as “bright burst galaxies,” less than 3000 light-years away.
These galaxies can create more than 1,000 stars like the Sun each year. To create such a large number of stars, the galaxy needs a large amount of gas and dust, which are essentially the building blocks of stars. In such galaxies, clouds of gas and dust kicked up by the rapid star formation can accumulate and completely obscure the quasars.
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The full study, published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS), estimates that in about 10-30% of very rapidly forming quasars, the host galaxy is solely responsible for obscuring the quasar.
The findings provide new insights into the connection between galaxy growth and black hole activity.
Fuzzy quasars may represent an early evolutionary stage, when young galaxies are rich in cold gas and dust, fueling high rates of star formation and black hole growth.
Professor David Alexander of Durham University, co-author of the study, said: “It’s a turmoil, a messy stage of evolution, where gas and stars collide and accumulate at the centre of the galaxy.”
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The discovery of these buried quasars will help scientists understand the connection between galaxies and the supermassive black holes that reside within them.
Source: phys.org
