One of the most enduring mysteries behind the dynamics of supermassive black holes, and their impacts on galactic evolution, has been uncovered by an international team of astrophysicists.
Using the ESO's Very Large Telescope (VLT), located in the Atacama desert in northern Chile, researchers from the UK, Netherlands and the US have studied the core of a nearby galaxy in great detail. The galaxy, called IC5063, has a very active central supermassive black hole that appears to drive rapid outflows of molecular hydrogen from the galaxy. IC5063 is known as a Seyfert galaxy, a very active type of galaxy with a bright core.
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Many active galactic nuclei have been observed with these outflow features and, as molecular hydrogen is key to the formation of stars, astronomers have realized that its ejection impacts star formation and, therefore, galactic evolution. As the majority of galaxies are thought to contain supermassive behemoths in their cores, the activity of these black holes (that have masses of tens to hundreds of millions of suns) can control the quantity of gas supplied to star forming regions.
But how do black holes accelerate this cold hydrogen gas to hundreds of thousands of miles per hour? Until now, that has been hard to fathom.
From the VLT observations, astronomers headed by Clive Tadhunter of the University of Sheffield have found that the outflow is driven by jets of relativistic electrons, which are being ejected from the dynamic environment just outside the black hole's event horizon. Whenever the highly energetic electrons blast through clouds of molecular hydrogen, the gas is transported out of the galaxy, starving it of star-forming material.
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"Much of the gas in the outflows is in the form of molecular hydrogen, which is fragile in the sense that it is destroyed at relatively low energies," said Tadhunter, who collaborated with researchers from the Netherlands Institute of Radio Astronomy and the Center for Astrophysics, Harvard. "It is extraordinary that the molecular gas can survive being accelerated by jets of electrons moving at close to the speed of light."
The research has been published in the journal Nature.
Interestingly, this study provides a small hint as to what our galaxy can expect when it collides with the neighboring Andromeda galaxy in around 5 billion years time. The merging of the two galaxies will inject matter into the central supermassive black holes, kick-starting powerful jets. When this occurs, would-be star-forming molecular gas will be ejected also, possibly stymieing star formation and changing the evolutionary outcome of our Milky Way.
Publication: Jet acceleration of the fast molecular outflows in the Seyfert galaxy IC 5063, Tadhunter et al., Nature, 2014. doi:10.1038/nature13520
Source: University of Sheffield