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A computational study of radio relics in galaxy cluster mergers / by Dane Patrick Owen.

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Call No.	QC45.N43 D3 2013owe
Author	Owen, Dane Patrick.
Title	A computational study of radio relics in galaxy cluster mergers / by Dane Patrick Owen.
Date	2013
Abstract	Radio relics are extended regions of synchrotron radio emission that have been found in the outskirts of a few dozen galaxy clusters. Relics are often associated with clusters undergoing merger activity. They are not associated optically with a particular member of the cluster and are thought to arise from relativistic electron populations in the intra-cluster medium. The radio phoenix model (Enßlin & Gopal-Krishna 2001), where shockwaves from merger activity re-energize a fossil radio plasma through adiabatic compression of the plasma, is one possible method of relic formation. This thesis uses gravitational N-body + SPH simulations (GADGET-2, Springel (2005)) with added synchrotron physics to present the largest computational study of radio relics in the radio phoenix model to date, totaling over 50,000 CPU-hours of computation and 4.7 TB of data. I have created a simulation data set of cluster mergers, with 25 different combinations of cluster mass, impact parameter, kinetic energies, cluster concentrations, and cluster-subcluster mass ratios. Using these simulations, I will discuss how high mass ratio collisions of 7:1 (cluster:subcluster mass) are most effective at reviving emission and creating a relic. I also show how this model predicts that clusters with total masses on the order of 6.25 x 10¹⁴M⊙ are most efficient at creating relics. By varying the magnetic pressure in the simulations, I demonstrate low relic formation is relatively insensitive to a wide range of magnetic field strengths. I also examine the great steepening of the spectral index of relics at even moderate (z ≈ 0.4) redshifts predicted by the simulations, with the implications for future low-frequency telescope arrays. Finally, I present specific merger simulations for the clusters Abell 85 and 2443. The relic emission in Abell 85 is shown to be well predicted by the radio phoenix model, while the possible merger of Abell 2443 with its subcluste ZwCL 2224.2+1651 is shown to be unlikely as the cause of the
Description	xxiv, 287 leaves : ill. (some col.) 28 cm.
Format	application/pdf
Advisor	Gary Wegner, Brian Chaboyer, John Thorstensen, Rose Finn
College	Dartmouth College. Department of Physics and Astronomy.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Copyright	All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means without permission in writing from the author.
DOI	http://dx.doi.org/10.1349/ddlp.996

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