Physical Properties of Clusters of Galaxies

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Jordan Toschak
Kevin Hannon and Megan Blanford
Physical Properties of Clusters of Galaxies
Monday (4/15/2013)

Procedure
For this experiment, a photograph of the Virgo Cluster of Galaxies will be needed to observe. The photograph will be sectioned into specific areas with coordinates like a map. Locate the area and identify the galaxies. Classify the galaxies as elliptical, spiral, or irregular. An elliptical galaxy will appear solid with not real defined “arms” or spirals coming from the center. An elliptical galaxy can be further classified E0 through E7 depending on the eccentricity of the elliptical. An elliptical galaxy with an E0 classification will be primarily rounded while an E7 will be remarkably eccentric. The classifications in between vary accordingly. A spiral galaxy will appear with a defined center or “bulge” with arms spiraling from the center. These classifications range from Sa to Sd. An Sa galaxy will have a large bulge with weak or small arms, an Sb galaxy will have a medium bulge and medium arms, an Sc galaxy will have a small bulge with large arms, and an Sd galaxy will have a bulge that isn’t clearly defined, but the stars are patterned in a circular manner. An irregular galaxy won’t look like any of these things, but there is a definite clump of stars. In addition to classifying each of these galaxies, measure the longest distance across the galaxy using the millimeter scale and the magnifying glass. If there is more than one galaxy in the coordinated area, measure each of them and average their sizes. Finally, average the apparent sizes of each of the spiral galaxies and use this measurement to determine the approximate distance to the Virgo Cluster of Galaxies using the equation Distance=2.2 million lightyears×78 mmN mm with N representing the average size of all of the spiral galaxies. Compare your results to the theoretical value D=16 Mpc (Mega parsecs) Use the conversion facts 1 pc=3.26 ly and 1 Mpc= 10X10⁶

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