Fabry-Perot Images of Spiral Galaxies
Some Fabry-Perot Images of Spiral Galaxies
- The first series of images refers to NGC 1672, a
barred spiral. We present a gray scale V-band image to show
the overall morphology, followed by an intensity map in H-alpha
which shows how the H II regions are distributed, followed by
the velocity map.
- Gray Scale V-band Image of NGC 1672:
- H-alpha Intensity Image of NGC 1672. Note how
the most intense regions of H-alpha emission are near the
ends of the bar (and in the nucleus).
- Velocity Field of NGC 1672. Different colors
refer to different velocities as the galaxy is rotating.
Note that the core also shows strong rotation.
The following image is an H-alpha intensity map of the spiral
galaxy NGC 1292. The Bright Red spots are prominent H II regions
and the blue represents more diffuse emission. Virtually every
place in the disk of this galaxy emits H-alpha radiation.
This next image is an H-alpha intensity map of the spiral galaxy
NGC 1406. Again, several prominent H II regions can be seen
near the center, while more diffuse emission is seen in the outer
This next image is the two dimensional velocity field, obtained
in the manner described above. The picture is coded so that
blue represents the part of the galaxy that is coming toward
us, as the disk rotates around a central point, and the red
represents that part of the disk which is rotating away from us.
The total rotation amplitude is about 150 km/s. Noticed the
detached red area, that represents a still higher velocity
H-alpha complex which may represent tidal debris or a small,
The graph represents points along a vector that goes from the center
of the galaxy out to the red edge. At each point along this vector,
a velocity is determined and hence this represents a crude rotation
curve. Notice that the rotation rises steeply near the center, and
then flattens out at large radii. This behavior is typical for
most spiral galaxies.
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