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Illustration of Active Galactic Nucleus
(Illustration: NASA/CXC/M.Weiss)


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CL 0542-4100:
Chandra Catches "Piranha" Black Holes



Credit: NASA/CXC/Ohio State Univ./J.Eastman et al

These two galaxy clusters, known as CL 0542-4100 and CL 0848.6+4453, are part of a sample used to count the fraction of galaxies with rapidly growing black holes, also known as active galactic nuclei (AGN). In the Chandra images of these two galaxy clusters, red corresponds to low-energy X-rays, the green to intermediate-energy, and the blue to high-energy X-rays. In each of these two fields, five AGN are found, although one of these may not be a member of the cluster. Many of the AGN are blue sources, as expected, since AGN are known to produce very high-energy X-rays. The diffuse emission is hot gas in the cluster and other point-like sources in the image are nearly all unrelated to the galaxy cluster.

The data show, for the first time, that younger, more distant galaxy clusters contained far more AGN than older, nearby ones. The four galaxy clusters in the distant sample, including the two shown here, are seen when the Universe is only about 58% of its current age. The nearby sample of galaxy clusters, obtained in an earlier study, is seen at about 82% of the Universe's current age. It was found that the more distant clusters contained about 20 times more AGN than the less distant sample. AGN outside clusters are also more common when the Universe is younger, but only by factors of two or three over the same age span.

The reason for this difference is that earlier in the history of the Universe, these galaxies contained a lot more gas for star formation and black hole growth than galaxies in clusters do today. There was so much fuel in young clusters that the piranha-like black holes were able to thrive by growing much earlier than their counterparts in nearby clusters.

Fast Facts for CL 0542-4100:
Credit  NASA/CXC/Ohio State Univ./J.Eastman et al
Scale  10.8 arcmin across.
Category  Quasars & Active Galaxies, Groups & Clusters of Galaxies
Coordinates (J2000)  RA 05h 42m 50.20s | Dec -41º 00' 6.98"
Constellation  Columba
Observation Dates  26 Jul 00
Observation Time  14 hours
Obs. IDs  914
Color Code  Red(0.3-1.0 keV); Green(1-2 keV); Blue(2-7 keV)
Instrument  ACIS
References Eastman J. et al, 2007, ApJ, Accepted
Distance Estimate  5.7 billion light years
Release Date  July 24, 2007
Fast Facts for CL 0848.6+4453:
Credit  NASA/CXC/Ohio State Univ./J.Eastman et al
Scale  10.8 arcmin across.
Category  Quasars & Active Galaxies, Groups & Clusters of Galaxies
Coordinates (J2000)  RA 08h 48m 55.90s | Dec +44º 54' 50.00"
Constellation  Lynx
Observation Dates  03 May 00 - 04 May 00
Observation Time  51 hours
Obs. IDs  927, 1708
Color Code  Red(0.3-1.0 keV); Green(1-2 keV); Blue(2-7 keV)
Instrument  ACIS
References Eastman J. et al, 2007, ApJ, Accepted
Distance Estimate  5.7 billion light years
Release Date  July 24, 2007