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Alive and well inside dwarf galaxies: Massive black holes

Wed, 01/08/2014 - 11:55am

Tiny dwarf galaxies can host massive black holes, according to researchers from Yale, Princeton and the National Radio Astronomy Observatory. Depicted here is NGC4395, a low mass galaxy with a known central black hole. Image courtesy of the researchers. Dwarf galaxies may be small, but astronomers now know that they can hold massive black holes.

Yale Univ. astronomer Marla Geha and collaborators have identified more than 100 dwarf galaxies that show signs of hosting massive black holes, a discovery that challenges the idea that they exist only in much bigger galaxies.

"These galaxies are comparable in size to the Magellanic Clouds, dwarf satellite galaxies of the Milky Way,” said Geha, assoc. prof. of astronomy. "Previously, such galaxies were thought to be too small to have such massive black holes.”

Dwarf galaxies are small, faint, low-mass galaxies with relatively few stars compared with, say, the Milky Way, Earth’s home galaxy. Black holes are points in space where matter is packed so densely that light itself cannot escape; massive black holes are an extreme form of black hole.

Geha and collaborators at the National Radio Astronomy Observatory (NRAO) and Princeton Univ. presented their findings during the American Astronomical Society’s annual meeting in Washington, D.C.

The scientists said that patterns of light emission from many of the galaxies suggest the presence of massive black holes. The black holes in the study are about 100,000 times the mass of Earth’s sun—massive, but vastly less dense than black holes seen in larger galaxies.

The research also offers new evidence for the origin of supermassive black holes, researchers said.

The team’s work is based on data from the Sloan Digital Sky Survey.

Source: Yale Univ.

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