Rain of giant gas clouds create active galactic nuclei

July 8, 2010, American Museum of Natural History

Galaxies like our own were built billions of years ago from a deluge of giant clouds of gas, some of which continue to rain down. Now new calculations tie the rain of giant clouds of gas to active galactic nuclei (AGN), the extremely bright centers of some galaxies. If a gas cloud with millions of times more mass than our Sun wanders too close to the center of a galaxy, it can either be consumed by the supermassive black hole that lurks there or, through shocks and collapse, give birth to new stars.

"For a while, people have known that gas clouds are falling onto galaxies, and they've also known that are powered by gas falling onto supermassive black holes," says Barry McKernan, a research associate in the Department of Astrophysics at the American Museum of Natural History and an assistant professor at the Borough of Manhattan Community College (BMCC), City University of New York. "But no one put the two ideas together until now and said, 'Hey, maybe one is causing the other!'"

All galaxies are believed to host a supermassive black hole at their center, yet only a fraction of galactic centers show signs of brighter activity due to black hole feeding. The new research provides an explanation for the apparent conundrum: galactic centers which have sustained recent cloud impacts have enough fuel to light up by giving birth to hundreds of and feeding the central black hole. Galactic centers that have not been hit for a while (in cosmic terms, for more than about 10 million years) will be relatively inactive and their cores will appear normal.

"It's interesting that only some galaxies are active, even though we think every galaxy contains a ," says K. E. Saavik Ford, a research associate at the Museum and an assistant professor at BMCC. "The cloud bombardment idea provides an explanation: it's just random luck."

Explore further: How do supermassive black holes get so big?

More information: The research paper, currently online, will be published in the Astrophysical Journal Letters.

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1 / 5 (3) Jul 09, 2010
Galaxies like our own may have been built giant clouds of gas. Or they may have been built by fragmentation of super-massive compact objects like giant neutron stars.

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
not rated yet Jul 09, 2010
Ok, Oliver, I'll play.

Let's ignore the fragmentation of a giant neutron star for a bit. How would this neutron star form? Perhaps from the collapse of a GMC? Certainly we can't have neutron stars as a primary building block of the universe.

Furthermore, are you suggesting a neutron star could contain as much mass as a universe? That'd be over the Tolman–Oppenheimer–Volkoff limit, no?
1 / 5 (2) Jul 09, 2010
Neutron repulsion may cause neutron emission and/or fragmentation of neutron stars, but prevent their collapse into a singularity (a black hole) [Journal of Fusion Energy 19 (2000) 93-98; Journal of Fusion Energy 20 (2001) 197-201]

Brown et al. observed and reported evidence of repeated fragmentation in the cosmos [Astrophysics & Space Science 72 (1980) 15-31; Astrophysics & Space Science 121 (1986) 351-355; Astrophysics & Space Science 123 (1986) 161-181; Astrophysics & Space Science 126 (1986) 255-267].

Harutyunian [Astrophysics 46 (2003, English) 81-91; Astrofizika 46 (2003, Russian) 103-118] noted that the steady production of stellar luminosity and the violent fragmentation of matter into clusters of stars and galaxies are similar to the steady decay and the violent fragmentation of unstable nuclei.

Neutron-emission and fragmentation of a neutron star are statistical processes, like the decay of ordinary nuclei via alpha, beta, gamma, or spontaneous fission

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