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.
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