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dc.contributor.authorQamar, Farid
dc.contributor.otherQueen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.))en
dc.date2014-09-16 10:00:42.457en
dc.date2014-09-16 13:11:18.328en
dc.date.accessioned2014-09-16T18:42:18Z
dc.date.available2014-09-16T18:42:18Z
dc.date.issued2014-09-16
dc.identifier.urihttp://hdl.handle.net/1974/12462
dc.descriptionThesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-09-16 13:11:18.328en
dc.description.abstractThe cause of varying galaxy interaction outcomes in different environments is investigated using a sample of over 505,000 Sloan Digital Sky Survey Data Release 7 galaxies at $0.01<z<0.20$. The aim is to distinguish the large-scale environmental effects on galaxies from the small-scale interaction effects in order to identify whether interaction mechanisms vary in different environments, or whether different galaxy populations produce the various outcomes in different environments. To study the properties of paired galaxies, the enhancements in star formation rates (SFRs) and asymmetries are investigated as functions of projected pair separations in different environments. The paired galaxies and control samples were selected using a new technique to distinguish between the influence of nearby neighbours and larger scale environment, and we define four different environmental classes using their dark matter halo masses (the field, poor groups, rich groups, and clusters). We find the strongest SFR enhancements at projected separations ($r_p$) $<40$ \hkpc~in field paired galaxies and the weakest (but statistically significant) in cluster paired galaxies, while the largest asymmetry enhancements are found in cluster paired galaxies, and the least in field paired galaxies. Using the asymmetry offset rather than enhancements reveals no dependence on environmental membership. Mean SFR suppression is found at separations $100<r_p<400$ \hkpc~for paired galaxies with mass ratio $<1$ in all environments, but is absent for paired galaxies with mass ratio $>1$. For paired galaxies with mass ratio $<1$, this suppression is accompanied by a lack of mean asymmetry offset or enhancement at similar separations. Possible explanations of this result include suppression due to an earlier encounter whereby star bursts consume the star forming gas, and given sufficient time the galaxy settles into a symmetric shape. At close separations ($r_p<40$ \hkpc), reduced mean SFR enhancements in all environments are found together with increased asymmetry enhancement in comparison with paired galaxies with mass ratio $>1$. We hypothesize that the suppression in lower-mass paired galaxies is due to the depletion of their gas reservoirs prior to the interaction, and conclude that interactions in different environments produce various results due to assembly bias rather than differing interaction mechanisms in various environments.en_US
dc.languageenen
dc.language.isoenen_US
dc.relation.ispartofseriesCanadian thesesen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectAstronomyen_US
dc.subjectAstrophysicsen_US
dc.subjectGalaxiesen_US
dc.subjectgalaxy interactionsen_US
dc.titleEnvironmental Effects on Interacting Galaxy Pairs in the SDSSen_US
dc.typethesisen_US
dc.description.degreeMasteren
dc.contributor.supervisorPatton, Daviden
dc.contributor.departmentPhysics, Engineering Physics and Astronomyen


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