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First Black Holes Were Lean and Mean
11 August 2009 (All day)
Like many pioneers in new surroundings, the first black holes found scant pickings, according to new simulations that mimic conditions in the early universe. The findings have scientists puzzling over how early black holes grew into the supermassive beasts they are today without a steady diet of gas, dust, stars, and other fodder.
Today's black holes thrive on recycled goods. Most galaxies abound with interstellar gas and dust, the detritus of countless generations of stars. Black holes grow by consuming material that passes too close to their enormous gravity wells. But fodder in the earliest universe was not nearly as plentiful, researchers at NASA; Stanford University in Palo Alto, California; and the Department of Energy's SLAC National Accelerator Laboratory in Menlo Park, California discovered. The team wanted to see how the earliest black holes grew, so they created simulations based on previous work with the earliest stars, many of which collapsed directly into the first black holes.
The simulations showed that the black holes radiated energy so intensely that they heated surrounding gas far into space--as far as 10,000 light-years away (see a movie here (22Mb)). The heated gas became so diffuse, it could not form nearby stars and solar systems, nor fall back inward to feed black holes. As a result, the team reports online this week in The Astrophysical Journal Letters, the earliest black holes grew less than 1% over 200 million years. It turns out that "a black hole's growth is limited until it is hosted by a larger galaxy," says astrophysicist and co-author John Wise of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The simulations "highlight for me how complex the processes in the early universe were," says astronomer Steven Willner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. In particular, he says, very little is known about what happened to the first stars or their remnants. "This paper is not the final word" on that process, Willner says, "but it's a very nice start."