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Astronomical Observatory: Cool Images

Astr212 Galaxy Projects, Spring 2007

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M86, Josh Stoep

M86

This is the galaxy M86; it is approximately 60,000 Kilo-light-years away and 113 kilo-light-years from end to end. M86 is an elliptical galaxy, as opposed to spiral, barred spiral or irregular. An elliptical galaxy is usually football shaped. Spiral galaxies are frisbee shaped with a bulge in the middle and arms spiraling outward from the center, which is what our own galaxy, the Milky Way, looks like. Barred spirals are similar except that the arms come out of the ends of a bar passing through the center bulge. Irregular galaxies can have many different shapes. Often, an irregular galaxy has collided with, or is being deformed by the gravitational field of another galaxy.

Elliptical galaxies such as this are shaped by random motions of the stars in them, as opposed to rotation like in spiral galaxies. Ellipticals range from dwarf ellipticals, 0.1Kpc, to over 100Kpc. the larger galaxies are often composed of globular clusters of stars. Ellipticals are generally yellowish red due to the average old age of the stars included in them. Ellipticals are classified according to shape. E0 are ellipticals which are almost perfectly spherical, E7 are elongated.

Charles Messier discovered M86 on March 18, 1781. This galaxy is found in the heart of the Virgo cluster along with the giant galaxies M87 and M84 among various others. Its relative motion of 419 km/sec toward us gives it the highest blueshift of all galaxies yet discovered.

In M86 the globular clusters are spread out giving it faint light to its edges. When you factor in the high blueshift of M86, you find that most of the stars in this galaxy are quite old and very little star formation is occurring. The overall old age of the galaxy tells us that there is little or no star formation happening. This is because there is very little interstellar gas in the galaxy so we can know that the light coming from the galaxy is due entirely to starlight.

M86 in X-ray

This is a composite image in the X-ray part of the spectrum (Blue), and the visible part of the spectrum (Orange). This shows a 200,000 Ly tail of gas being pulled from inside the galaxy toward the center of the Virgo cluster. X-ray images visually show this invisible part of the electromagnetic spectrum. Hot gas emits X-ray radiation as shown in this image. From this image we can see that there is a relatively small amount of gas inside the galaxy and it also shows that there must be a strong gravitational attraction pulling the gas out. This attraction is also why the galaxy M86 has an extremely high blueshift. It is being pulled towards us by the gravitational center of the Virgo cluster.

M86 Light Profile Major Axis

M86 Light Profile Minor Axis

These are graphs of the major and minor axis respectively, of the light profile of M86. It shows the luminosity as a function of the radius. When working with elliptical galaxies, we want to find the general trend of luminosity as it relates to the radius. Where the line fits the profile represents the section of the galaxy between the center and the very edges where the luminosity drops off with radius. The line has an equation of y = -2.2289x + 5.3254.

Data Reduction:

These images were calibrated with Bias Dark and Flat images. Each filter was then aligned and median combined. The best images in each filter were then combined and color combined to give me an LRGB image with red at 0.65 green 0.58 and blue 3.5. I then saved it as a JPEG after adjusting the Gamma value to 0.3.

References:

"M86" Chandra x-Ray Observatory

Kutner, Marc L. Astronomy: A Physical Perspective. 2nd ed. Cambridge, United Kingdom: Cambridge University Press, 2003.

"M86" SEDS

Right Ascension (J2000) 12:26:11
Declination (J2000) +12:56:46
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 300 s in B and V, 60 and 180s in R, 60s in C
Date observed

February 21, 2007; March 3, 2007; March 13, 2007

 

 

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