A Lenticular Galaxy, Kristin Datema
Galaxies are large
groupings of stars that can contain hundreds of billions of stars. One
such galaxy is M85
(right), which is a lenticular (SO) galaxy. Lenticular
galaxies are galaxies that are neither completely elliptical
galaxies. Elliptical galaxies appear to be smooth and have an elliptical
shape, but have no spiral structure. Spiral galaxies, on the other hand,
have disks and a spiral structure within their disks. A lenticular
is a combination of an elliptical and a spiral galaxy. Lenticular galaxies
have a disk, but do not have a
spiral structure in the disk. Often lenticular
galaxies are misclassified as ellipticals because then tend to
more as ellipticals than spirals. In this image the disk structure is
hard to see, but it has a vertical orientation. Some lenticular galaxies
have a much more prominent disks. For example, NGC
5866 has a
clearly visible disk. Also in the image NGC 4394 (left)
is a small barred spiral galaxy. From the image it is
apparent that NGC
4394 has a spiral structure whereas M85 does not. These galaxies do have
for instance both M85 and NGC 4394 have disks even though
it is not so apparent in the image.
M85 was discovered
in 1781 by Pierre Mechain. The name M85 came from Charles Messier who
galaxy to his famous catalogue. M85 is located approximately
59 million light years away from the earth. This particular galaxy is
the northernmost member of the Virgo Cluster of galaxies and it can be
found in the constellation Coma Berenices. In the image, M85 appears to
have a yellowish tint because it contains an old
yellow stellar population.
The stars are yellow because they are long-lived stars which are low temperature
stars and are therefore towards the red end of the spectrum.
In the above image
the contours are x-ray and the gray scale is the optical negative. M85
is the dark spot in
the middle. This x-ray image shows the supernova remnants
and ionized hydrogen. The light detected by this image is emitted through
synchrotron radiation. This means that there were supernovae in M85 in
In fact, according to S.E.D.S., there was a supernova in M85
and it appeared in 1960.
The above image is
a Near Infrared image of M85. The colors in this image show three infrared
1.25, 2.2, and 3.5 microns. The objects seen in this image
come from the blackbody emission of the K, F,
and M stars. These are the
older and cooler stars in the bulge of the galaxy. This image therefore
M85 does indeed contain older stars.
This graph is the
light profile for the major axis of M85. A light profile is a plot of
the brightness of a galaxy at certain radii. This is important for an
elliptical galaxy because it can be used to determine an effective radius.
The effective radius is of interest because inside that radius, half the
total light given off by the galaxy is
emitted. The data was analyzed
and a light curve was created using Microsoft Excel. The equation of best
was y = -1.251x + 5.774, where y = log(surface brightness) and x =
(radius)^(1/4). From this data the effective radius and the ellipticity
can be calculated. The effective radius of the major axis was 100.54 arc
with an uncertainty of .06 arc seconds. The ellipticity of M85
was calculated to be n=1.2.
Elmegreen, D.M. 1998, Galaxies and Galactic Structure (New Jersey: Prentice
Fabbiano, G.; Kim,
D.-W.; Trinchieri, G., "An
X-ray catalog and atlas of galaxies", 1992, Astrophysical Journal
Supplement Series, 80, 531
Jarrett, T. H; Chester,
T.; Cutri, R.; Schneider, S. E.; Huchra, J. P."The
2MASS Large Galaxy Atlas", 2003, Astronomical Journal, 125, 525
Kutner, M. L. 2003,
Astronomy: A Physical Perspective, 2nd ed. (Cambridge: Cambridge University
Students for the
Exploration and Development of Space, M85.
This research has
made use of the NASA/IPAC
Extragalactic Database (NED) which is operated by the Jet Propulsion
Laboratory, California Institute of Technology, under contract with the
National Aeronautics and
is in the constellation Coma Berenices. North is up and East is
to the left.
||The image is 12.1 by 8.7 arc minutes, which
is 207,000 by 149,000 light years at the distance M85.
|Dates of observation
|| The Maxim program was used in each step of the reduction of all
the data. First all the data was calibrated using a bias, dark and
a flat to remove noise. The clear images were aligned and combined
using the median combine. Then each of the blue, green and red filter
images were aligned and the images of each color were median combined.
Then the clear, blue, green and red images were color combined.
The color was adjusted until the true color of the galaxy was seen.
Then the gamma stretch function was used to bring out details of
the galaxy without overexposing the core of the galaxy.