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).
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.
","abstract_html":"<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>","abstract_has_math":false,"creators":["Fultz, Kayla Jo"],"institution":"Ohio University Art and Sciences Honors Theses","degree_name":"Bachelor of Sciences","degree_level":"bachelors","degree_discipline":"Physics and Astronomy","degree_department":null,"school":null,"contributors":["Clowe, Douglas"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2010,"date_issued":"2010","date_published":"2010","updated_at":"2026-07-24T03:36:08Z","subjects":["Astronomy","Astrophysics","Physics","galaxy clusters","mass measurement","redshift","sloan digital sky survey","timing argument"],"languages":["English"],"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."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://rave.ohiolink.edu/etdc/view?acc_num=ouashonors1276622097","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Clowe, Douglas"]},{"key":"dc:creator","label":"Author","values":["Fultz, Kayla Jo"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2010"]},{"key":"dc:publisher","label":"Institution","values":["Ohio University Art and Sciences Honors Theses / OhioLINK"]},{"key":"dc:type","label":"Dc Type","values":["Electronic Thesis or Dissertation"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics and Astronomy"]},{"key":"thesis:degree_level","label":"Degree Level","values":["bachelors"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Bachelor of Sciences"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Ohio University Art and Sciences Honors Theses"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Astronomy","Astrophysics","Physics","galaxy clusters","mass measurement","redshift","sloan digital sky survey","timing argument"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]},{"key":"dc:rights","label":"Dc Rights","values":["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."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://rave.ohiolink.edu/etdc/view?acc_num=ouashonors1276622097"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["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).
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.
"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf","p.30","706.2 KB"]},{"key":"dc:title","label":"Title","values":["A New Mass Measurement for Galaxy Clusters Using Position and Radial Velocity"]}]}],"canonical_facts":{"dc:contributor":["Clowe, Douglas"],"dc:creator":["Fultz, Kayla Jo"],"dc:date":["2010"],"dc:description":["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).
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.
"],"dc:format":["application/pdf","p.30","706.2 KB"],"dc:identifier":["http://rave.ohiolink.edu/etdc/view?acc_num=ouashonors1276622097"],"dc:language":["English"],"dc:publisher":["Ohio University Art and Sciences Honors Theses / OhioLINK"],"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."],"dc:subject":["Astronomy","Astrophysics","Physics","galaxy clusters","mass measurement","redshift","sloan digital sky survey","timing argument"],"dc:title":["A New Mass Measurement for Galaxy Clusters Using Position and Radial Velocity"],"dc:type":["Electronic Thesis or Dissertation"],"thesis:degree_discipline":["Physics and Astronomy"],"thesis:degree_level":["bachelors"],"thesis:degree_name":["Bachelor of Sciences"],"thesis:institution_name":["Ohio University Art and Sciences Honors Theses"]},"updated_at":"2026-07-24T03:36:08Z"}