Mystery of the Missing Black Holes Solved

Don't talk to me about Sherlock Holmes. A rank amateur. What kind of massive, mysterious stellar formation did he ever find, answer me that.

No, try this story instead: Scientists working with NASA's Spitzer and Chandra space telescopes have discovered hundreds of black holes hiding in the middle of young, dusty galaxies often billions of light years away, solving a puzzle that had previously left scientists wondering.

Many galaxies, including the Milky Way itself, are thought to have huge black holes at their center. Yet scientists have believed that there ought to be far more quasars, or massive black holes surrounded by gas and dust, than they had observed.

An international team of researchers recently set out to study the problem, observing 1000 distant galaxies which were about the same mass as our own, but were apparently hole-less. At between 9 and eleven billion light years away, these were all about 2.5 billion to 4 billion years old, dating from when the universe was much younger.

In their observations, the team noted that about 200 of the galaxies were giving off far more infrared light than would be expected. A little creativity, combining Spitzer's infrared with Chandra's X-ray observations, unveiled what turned out to be "plump" quasars sitting inside.

"Active, supermassive black holes were everywhere in the early universe," said Mark Dickinson of the National Optical Astronomy
Observatory in Tucson, Ariz. "We had seen the tip of the iceberg before in our search for these objects. Now, we can see the iceberg itself."

The discovery certainly helps fill the previously unexplained gap in the black hole population, and is already helping researchers understand more about the formation of big galaxies.

The findings are the first direct evidence that virtually all big galaxies in the universe's early days had huge black holes at their core, researchers said. They've further deduced, they say, that galaxies the size of the Milky Way build up black holes and stars simultaneously during their early lives, until the black holes begin to undermine star formation.

A pair of papers describing the observations and subsequent analyses will be published in the Nov. 10 issue of *Astrophysical Journal. *

Missing Black Hole Report: Hundreds Found! [NASA JPL press release]

(Image: An infrared image of the distant universe from Spitzer. The galaxies circled in blue have black holes at their cores. Credit: NASA/JPL-Caltech/Commissariat a l'Energie Atomique)**