|
|
HCG 62:
Chandra Captures Remarkable Image of Galaxy Group
A new Chandra image shows remarkable detail and
complexity in the central region of the compact galaxy
group known as HCG 62. Such galaxy groups, which
contain fewer galaxies than the better-known galaxy
clusters, are an important class of objects because
they may serve as cosmic building blocks in the
large-scale structure of the universe. After galaxies
themselves form in the early universe, such groups of
galaxies may be the next systems to evolve. Later, it
is believed, these groups of galaxies may combine with
each other to form the bigger galaxy clusters. Most
galaxies in the present-day universe are still in
groups or poor clusters. Our own Milky Way Galaxy,
along with about two dozen other galaxies, including
the Andromeda Nebula (M31) and the Large and Small
Magellanic Clouds, is part of a galaxy group known as
the Local Group.
A team of scientists, led by Jan Vrtilek
(Harvard-Smithsonian Center for Astrophysics), observed
HCG 62 with Chandra for about 50,000 seconds with the
Advanced CCD Imaging Spectrometer. The range of X-ray
surface brightness is represented in this image by
various colors: green depicts the lower-brightness
regions while purple and reddish indicate increasing
X-ray intensity. The image is about four minutes of arc
on a side, with north to the top and east to the
left.
Chandra is an excellent tool to study the intragroup
gas (the material between the galaxies) since this
medium is too hot (roughly ten million degrees Celsius)
to emit any significant radiation at optical
wavelengths, but instead radiates most strongly in
X-rays. Chandra also offers by far the highest angular
resolution of any X-ray telescope to date, which is
essential for showing the detailed structure of a
complex source such as HCG 62. Hence, this X-ray
observation provides a unique window for determining
the physical characteristics of the galaxy group.
Perhaps the most striking features of this X-ray image
of HCG 62 are the two cavities that appear nearly
symmetrically opposite one another (upper left and
lower right) in the hot, X-ray emitting gas. These
cavities might be explained by the presence of X-ray
absorbing material, but are more likely due to jets of
particles recently emitted from the core of NGC 4761,
the central elliptical galaxy of HCG 62, although no
such jets are visible today.
| Fast Facts for HCG 62: |
| Credit |
NASA/CfA/J. Vrtilek et al. |
| Scale |
Image is 4 arcmin on a side. |
| Category |
Groups & Clusters of Galaxies |
| Coordinates (J2000) |
RA 12h 53m 08.10s | Dec -09° 13' 27.00" |
| Constellation |
Virgo |
| Observation Dates |
January 25, 2000
|
| Observation Time |
8 hours |
| Color Code |
Intensity |
| Instrument |
ACIS |
| Distance Estimate |
About 200 million light years |
| Release Date |
March 05, 2001 |
|
|
|
