Black holes may precede galaxies, astronomers say

WASHINGTON (Reuters) - Black holes -- those massive, invisible objects that suck in everything around them -- may have appeared before the galaxies that host them, astronomers said on Wednesday.

The findings could change the understanding of how galaxies first formed, and what role black holes play in the universe.

Most or all galaxies are believed to have black holes at their centers. Just last month astronomers confirmed that our own Milky Way galaxy has a black hole at its center.

Researchers told a meeting of the American Astronomical Society in Long Beach, California, that they had seen a clear link between the size of a black hole, as measured by its mass, and the galaxy where it was found.

A black hole's mass is about one one-thousandth of the mass of the surrounding galactic bulge, they said.

"This constant ratio indicates that the black hole and the bulge affect each others' growth in some sort of interactive relationship," said Dominik Riechers of the California Institute of Technology, or Caltech.

"The big question has been whether one grows before the other or if they grow together, maintaining their mass ratio throughout the entire process."

The researchers used the Very Large Array telescope in New Mexico and other instruments to compare nearby, and younger, black holes to those that are farther away and thus older. They have seen back close to the Big Bang, 13.7 billion years ago.

"We finally have been able to measure black-hole and bulge masses in several galaxies seen as they were in the first billion years after the Big Bang, and the evidence suggests that the constant ratio seen nearby may not hold in the early universe," said Fabian Walter of the Max-Planck Institute for Radioastronomy in Germany.