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Elliptical Galaxy Gallery: Black Holes Stir Up Galaxies
Chandra images of 56 elliptical galaxies have revealed evidence for
unsuspected turmoil. As this sample gallery of X-ray (blue & white) and
optical (gray & white) images shows, the shapes of the massive clouds of
hot gas that produce X-ray light in these galaxies differ markedly from
the distribution of stars that produce the optical light.
Except for rare cases, most violent activity in isolated elliptical
galaxies was thought to have stopped long ago. Elliptical galaxies
contain very little cool gas and dust, and far fewer massive young stars
which explode as supernovas. Thus it was expected that the hot
interstellar gas would have settled into an equilibrium shape similar
to, but rounder than that of the stars.
Surprisingly, this study of elliptical galaxies shows that the
distribution of hot gas has no correlation with the optical shape. A
powerful source of energy must be pushing the hot gas around and
stirring it up every hundred million years or so.
Although supernovas are a possible energy source, a more probable cause
has been identified. The scientists detected a correlation between the
shape of the hot gas clouds and the power produced at radio wavelengths
by high-energy electrons. This power source can be traced back to the
supermassive black hole in the galaxies' central regions.
Repetitive explosive activity fueled by the infall of gas into the
central supermassive black hole is known to occur in giant elliptical
galaxies located in galaxy clusters. Scientists' analysis of the Chandra
data indicates that the same phenomena are occurring in isolated
elliptical galaxies as well.
| Fast Facts for Elliptical Galaxy Gallery: |
| Credit |
X-ray: NASA/CXC/U. Ohio/T.Statler & S.Diehl; Optical: DSS |
| Category |
Normal Galaxies & Starburst Galaxies |
| Color Code |
Intensity |
| Instrument |
ACIS |
| References | T. Statler and S.Diehl, 2006, "Morphology of the Hot ISM in Normal Elliptical Galaxies: A Chandra Gas Gallery" Bulletin of the American Astronomical Society |
| Release Date |
January 10, 2006 |
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