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Donald Savage
Headquarters, Washington           May 21, 2003
(Phone: 202/358-1727)

Steve Roy
Marshall Space Flight Center, Huntsville, Ala.
(Phone: 256/544-6535)

Megan Watzke
Chandra X-ray Observatory Center, CfA, Cambridge, Mass.
(Phone: 617/496-7998)

RELEASE: 03-173

CHANDRA PROVIDES NEW VIEW OF BIGGEST CONSTRUCTION SITES IN 
UNIVERSE

     Images made by NASA's Chandra X-ray Observatory have 
revealed two distant cosmic construction sites buzzing with 
activity. This discovery shows how super massive black holes 
control the growth of massive galaxies in the distant 
universe. 

X-rays were detected from vast clouds of high-energy 
particles around the galaxies 3C294 and 4C41.17, which are 
10 and 12 billion light-years from Earth, respectively. The 
energetic particles were left over from past explosive 
events that can be traced through the X-ray and radio jets 
back to the super massive black holes located in the centers 
of the galaxies. 

"These galaxies are revealing an energetic phase in which a 
super massive black hole transfers considerable energy into 
the gas surrounding the galaxies," said Andrew Fabian of 
England's Cambridge University, lead author of a paper on 
3C294 to appear in an upcoming issue of the Monthly Notices 
of the Royal Astronomical Society. "This appears to be 
crucial in explaining the puzzling properties of present-day 
galaxies, especially those that group together in large 
clusters," he said. 

The picture that is emerging is of a grand cosmic cycle. A 
dense region of intergalactic gas cools to form several 
smaller galaxies, which merge to form a larger galaxy with a 
super massive black hole. The galaxy and its central black 
hole continue to grow until the energy generated by jets 
from the vicinity of the voracious black hole stops the fall 
of matter into the black hole. Millions of years after the 
jet activity subsides, matter will resume falling into the 
black hole and the cycle begins anew.

Both 3C294 and 4C41.17 reside in regions of space containing 
unusually high numbers of galaxies. The gas and galaxies 
surrounding these galaxies will eventually collapse to form 
galaxy clusters, some of the most massive objects in the 
universe. Although 3C294 and 4C41.17 will grow to gargantuan 
sizes, through the accumulation of surrounding matter that 
forms hundreds of billions of stars, their growth does not 
go unchecked. 

"It's as if nature tries to impose a weight limit on the 
size of the most massive galaxies," said Caleb Scharf of 
Columbia University, New York, and lead author of a paper on 
4C41.17 to be published in The Astrophysical Journal. "The 
Chandra observations have given us an important clue as to 
how this occurs. The high-energy jets give the super massive 
black holes an extended reach to regulate the growth of 
these galaxies," he said.

In 3C294 and 4C41.17, the hot swirling infernos around their 
super massive black holes have launched magnetized jets of 
high-energy particles first identified by radio telescopes. 
These jets, which were also detected by Chandra, have swept 
up clouds of dust and gas and have helped trigger the 
formation of billions of new stars. The dusty, star-forming 
clouds of 4C41.17, the most powerful source of infrared 
radiation ever observed, are embedded in even larger clouds 
of gas.  

Astronomers recently used the Keck Observatory to observe 
these larger clouds, which have a temperature of 10,000 
degrees. These clouds are leftover material from the 
galaxy's formation and should have cooled rapidly by 
radiation in the absence of a heat source.

"Significantly, the warm gas clouds coincide closely with 
the largest extent of the X-ray emission," said Michiel 
Reuland of Lawrence Livermore National Laboratory, 
Livermore, Calif., a coauthor on the 4C41.17 paper and a 
paper describing the Keck Observatory work. "The Chandra 
results show that high-energy particles or radiation can 
supply the necessary energy to light up these clouds," he 
said. 

Most of the X-rays from 4C41.17 and 3C294 are due to 
collisions of energetic electrons with the cosmic background 
of photons produced in the hot early universe. Because these 
galaxies are far away, their observed radiation originated 
when the universe was younger and the background was more 
intense. This effect enhances the X-radiation and helps 
astronomers to study extremely distant galaxies. 

NASA's Marshall Space Flight Center, Huntsville, Ala., 
manages the Chandra program. TRW, Inc., Redondo Beach, 
Calif., is the spacecraft prime contractor. The 
Smithsonian's Chandra X-ray Center controls science and 
flight operations from Cambridge, Mass., for the Office of 
Space Science, NASA Headquarters, Washington.

Images and information are available at:

http://chandra.harvard.edu & http://chandra.nasa.gov

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