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Object: Radio Galaxy 3C324
and Surrounding Clusters of Galaxies
Telescope and Focus: Subaru Telescope
(Effective diameter 8.2m), Cassegrain Focus
Instrument: CISCO (Cooled Infrared
Spectrograph and Camera for OHS)
Filter: Near Infrared K'-band (2.15
microns)
Colors: red - Subaru Telescope, Near
Infrared K'-band (2.15 microns)
green- Hubble Space Telescope WFPC2, red visible light
(F702W)
blue - Hubble Space Telescope WFPC2, blue visible
light (F450W)
Date of Observation: April 2, 1999
UT. (HST observations are from the STScI archive)
Exposure Time: 800 sec
Field of View: 1.5 arcmin by 2 arcmin
Image Orientation: North is towards
upper right (38 degree to the right of vertical);
East is towards upper left.
Coordinates (J2000.0): RA=17h 14m 10s, DEC=+50 deg
16' (in the constellation of Draco) |
Explanation:
An active galaxy and clusters of other distant galaxies
are clearly revealed when an infrared image obtained with
the recently completed Subaru Telescope is combined with
Hubble Space Telescope (HST) images taken in visible light.
The small object with tangled red and blue
colors near the field center is the active galaxy 3C324.
Its enlarged image shown in the inset provides a new view
of the galaxy. The active galaxy, emitting strong radio
noise, is located 10 billion light years away and displays
strong optical jets revealed by Hubble Space Telescope.
The inner-most two blue-white "beads" seen in
the inset are the two jets of material flowing outward in
opposite directions from a central source. Centered on and
surrounding the jets is the diffuse reddish glow of the
active radio galaxy itself, revealed clearly here by Subaru
Telescope. It appears to be an elliptical galaxy. We are
seeing this galaxy while it is going through a phase of
great activity at a time when the Universe was still very
y oung and less than half of its present size.
A dozen red patchy objects seen near the
center and to the upper right are members of very distant
clusters of galaxies, one of which is thought to be distributed
around 3C324. Blue objects are foreground galaxies and stars
well detected with Hubble Space Telescope, while the red
objects are galaxies barely seen in the visible-light images
of Hubble Space Telescope. The tremendous light-gathering
power of Subaru Telescope combined with its ability to produce
infrared imaging at a resolution approaching that of HST
allows us to clearly see sharp and bright details in these
faint infrared galaxies. Note that these galaxies appear
relatively bright in the infrared because they have long
ago finished active star formation (i.e.- now mostly composed
of cooler reddish stars) as well as because their starlight
is strongly redshifted (z = 1.2) due to the expansion of
the Universe.
The resolution of the Subaru Telescope
infrared observations used to make this color composite
is about 0.36 arcsec. The two HST images used in making
this composite originally had a resolution of ~0.15 arcsec
and were slightly blurred before combining with the Subaru
Telescope image. Also note that the HST data doesn't quite
cover the whole image, hence the total lack of blue or green
colors in the top right corner (beyond the dotted line).
The HST images were created with the support
of the Space Telescope Science Institute, operated by the
Association of Universities for Research in Astronomy, Inc.,
from NASA contract NAS5-26555
June 10, 1999 |
