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GOODS Chandra Deep Field South:
GOODS Missing Black Hole Report: Hundreds Found!
The artist's illustration on the left shows a typical massive galaxy as it
would have appeared when the universe was only about a quarter of its
current age. This young galaxy contains an active galactic nucleus (AGN), or quasar,
in its center, a luminous object powered by the rapid growth of a
supermassive black hole. Some of the light from the AGN is obscured by dense
gas and dust near the center of the galaxy. The galaxy itself is
undergoing a growth spurt, as shown by bright regions of star formation in
the spiral arms.
Spitzer Space Telescope observations are extremely efficient at detecting
distant AGN like this because dust and gas should absorb high-energy
radiation from the AGN and re-emit it at longer wavelengths, generating
copious amounts of infrared emission. Large numbers of galaxies thought to
contain such highly obscured AGN have been discovered in the Great
Observatories Origins Deep Survey. The infrared emission for these
galaxies exceeds the levels likely to be caused by star formation. However,
X-ray observations were required to confirm the presence of obscured AGN,
by looking for the high energy X-rays expected from such objects (less
energetic X-rays are mostly absorbed).
The image on the right shows a "stacked" Chandra X-ray Observatory image of
distant, massive galaxies detected with the Spitzer Space Telescope. Image
stacking is a procedure used to detect emission from objects that is too
faint to be detected in single images. To enhance the signal, images of
these faint objects are stacked on top of one another.
In this image, low-energy X-rays are shown in orange and high-energy X-rays
in blue, and the stacked object is in the center of the image (the other
sources beyond the center of the image are individual AGN that were
directly detected and are not part of the source stacking). The blue
stacked source confirms the hypothesis that large numbers of these young,
massive galaxies contain heavily obscured AGN.
Spitzer also detected infrared emission from young, massive galaxies that
is consistent with expectations for star formation. These galaxies do not
contain AGN, because their supermassive black holes are dormant. A stacked
Chandra image of these "normal" massive galaxies shows mainly soft X-ray
emission at the center, as expected.
| Fast Facts for GOODS Chandra Deep Field-South: |
| Credit |
Illustration: NASA/JPL-Caltech/T.Pyle (SSC); X-ray: NASA/CXC/Durham/D.Alexander et al.; Infrared: NASA/JPL-Caltech/CEA/E.Daddi |
| Scale |
Right panel is
25 arcsec across |
| Category |
Cosmology/Deep Fields/X-ray Background, Black Holes, Quasars & Active Galaxies |
| Coordinates (J2000) |
RA 03h 32m 28s | Dec -27'º 48' 30.00'' |
| Constellation |
Fornax |
| Observation Date |
11 pointings from Oct 1999 - Dec 2000
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| Observation Time |
278 hours |
| Obs. ID |
1431_0, 1431_1, 441, 582, 2406, 2405, 2312, 1672, 2409, 2313, 2239
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| Color Code |
Energy (Orange: 0.5-2 keV; Blue: 2-8 keV) |
| Instrument |
ACIS |
| References | Daddi et al, 2007, ApJ, in press |
| Distance Estimate |
Galaxies are about 9 to 11 billion light years |
| Release Date |
October 25, 2007 |
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