Massive black holes and new stars forming at the center of many large galaxies may feed from the same trough of gaseous material as they grow, according to a new study.
A team of four scientists found evidence that the massive black holes at the center of four distant but extremely bright galaxies formed from the same primordial clouds of gas that fed the stars in their respective bulges. The black holes in these bright galaxies are actively consuming matter and are known as active galactic nuclei, or AGNs.
The findings hold true for both elliptical galaxies and spiral galaxies, the researchers say.
Because of the time taken for their light to reach Earth, the galaxies in the new study appear to have been forming stars and massive black holes when the universe was about a third of its current age, assuming it is about 12.5 billion years old today. Some researchers say the universe may be older than that.
The idea of simultaneous formation of black holes and stars that make up the bulges in spiral and elliptical galaxies is not new. In the past, scientists have seen a correlation between the masses of massive black holes and galactic bulges, and some believe that the development of bulges and central black holes go hand-in-hand.
Elliptical galaxies and the bulges of spiral galaxies are commonly called galactic spheroids. Galactic bulges are dense concentrations of stars roughly in the shape of a sphere around the center of a galaxy. The Milky Way, like many large spiral galaxies, has a bulge, though many smaller galaxies do not.
Recent evidence has shown that galaxies without bulges of stars at their centers do not have a black hole at their core.
The study appeared Nov. 1 in the online publication Science Express, a web-based version of the print journal Science that allows for more rapid publication of findings. Scientists involved with the current research said their goal was to see whether the correlation between the formation of massive black holes and bulges could be expressed simply in that they shared the same source of material while forming.
Mat Page, of the Mullard Space Science Laboratory at the University of London and one of the researchers in the study, said the difficulty in observing the tandem development of galaxy bulges and central black holes of active galactic nuclei is possibly due to surrounding clouds of dense gas and dust.
These clouds, he said, can hide what goes on inside them from telescopes.
Page and his fellow researchers used the Submillimeter Common User Bolometer Array (SCUBA) mounted on the James Clark Maxwell Telescope in Hawaii to observe the galaxies included in their study. The array measures radiation emitted at submillimeter wavelengths, which are longer than infrared, shorter than radio waves and invisible to the naked eye, using detectors cooled to a temperature near absolute zero (-273 degrees Celsius).
Out of eight galaxies initially chosen for observation, only four were extremely bright in the submillimeter wavelengths, allowing researchers to detect their emissions from dust heated by young stars, implying high rates of star formation, according to the scientific paper written by Page and his colleagues.
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