A New Mass Measurement for Galaxy Clusters Using Position and Radial Velocity

<p>Galaxy clusters are the largest structures in the Universe, and the evolution ofgalaxy cluster mass profiles is a useful tool for constraining cosmological models. Mostmethods established for obtaining a mass profile of a cluster of galaxies assumes theclusters obey the virial theorem; however, the majority of clusters are observed to containnon-virialized substructures. Zaritsky outlined a timing argument for obtaining massprofiles (Zaritsky, 1989). The timing argument assumes that at a time t = 0, every galaxyin the cluster was concentrated at one point, and then simultaneously exploded outward.The current position of each galaxy with respect to the cluster center is determined onlyby Newtonian gravitation. Zaritsky applied this method to the local group and obtainedreasonable mass profiles (Zaritsky, 1989).</p><p>We test this new method for mass measurement and compare our results to valuesobtained using virialized methods. We apply this timing argument to a sample of galaxyclusters of nearby redshift (from z~0.05 to z~0.2) taken from the Sloan Digital SkySurvey, using a 12 Mpc radius (a region larger than the typical infall radius) for eachcluster. We chose clusters from a paper written by Popesso that contained publishedvelocity dispersions for each cluster (Popesso, 2006). The profiles we acquire through thetiming argument have a useful astronomical application because they rely only oninfalling galaxies in the cluster, forgoing the virial theorem. We estimate a mass based onthese profiles and use that mass to calculate a velocity dispersion in each cluster. Ourvelocity dispersions are compared to published values. Our comparison shows that thismethod for mass measurement gives reasonable velocity dispersions when applied to alarge sample of galaxies. There is no clear systematic offset between our data set and thepublished data set, and many variables within this method leave room for large errors.</p>

Name thesis:degree_name

Bachelor of Sciences

Level thesis:degree_level

bachelors

Discipline thesis:degree_discipline

Physics and Astronomy

Grantor dc:publisher

Ohio University Art and Sciences Honors Theses

Year dc:date

2010

Author dc:creator

• Fultz, Kayla Jo

Contributors dc:contributor

• Clowe, Douglas

• Astronomy
• Astrophysics
• Physics
• galaxy clusters
• mass measurement
• redshift
• sloan digital sky survey
• timing argument

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=ouashonors1276622097

OAI identifier oai:identifier

oai:etd.ohiolink.edu:ouashonors1276622097