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 active galactic nuclei 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 stars 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 supermassive black hole," 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."
The research paper, currently online, will be published in the Astrophysical Journal Letters. In addition to McKernan and Ford, the paper is authored by Ari Maller, assistant professor at New York City College of Technology, City University of New York. The research was supported in part by the American Museum of Natural History, grants from the City University of New York, and an ROA supplement to a National Science Foundation grant.
Kristin Elise Phillips | EurekAlert!
Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University
Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences