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dc.contributor.authorBanik, Indranil
dc.contributor.authorZhao, Hongsheng
dc.identifier.citationBanik , I & Zhao , H 2015 , ' Effects of lens motion and uneven magnification on image spectra ' , Monthly Notices of the Royal Astronomical Society , vol. 450 , no. 3 , pp. 3155-3168 .
dc.identifier.otherPURE: 241630656
dc.identifier.otherPURE UUID: 2a226004-e0a1-4e72-aa2a-c07ca12b7cb9
dc.identifier.otherRIS: urn:5BF4B68CB0C3ECD45C427AC34AE49DCD
dc.identifier.otherScopus: 84930826636
dc.identifier.otherORCID: /0000-0002-4123-7325/work/29616906
dc.identifier.otherWOS: 000356339300067
dc.descriptionIB is supported by a Science & Technology Facilities Council studentship.en
dc.description.abstractCounter to intuition, the images of an extended galaxy lensed by a moving galaxy cluster should have slightly different spectra in any metric gravity theory. This is mainly for two reasons. One relies on the gravitational potential of a moving lens being time dependent (the moving cluster effect, MCE). The other is due to uneven magnification across the extended, rotating source (the differential magnification effect, DME). The time delay between the images can also cause their redshifts to differ because of cosmological expansion. This differential expansion effect is likely to be small. Using a simple model, we derive these effects from first principles. One application would be to the Bullet Cluster, whose large tangential velocity may be inconsistent with the Λ cold dark matter paradigm. This velocity can be estimated with complicated hydrodynamic models. Uncertainties with such models can be avoided using the MCE. We argue that the MCE should be observable with Atacama Large Millimetre Array. However, such measurements can be corrupted by the DME if typical spiral galaxies are used as sources. Fortunately, we find that if detailed spectral line profiles were available, then the DME and MCE could be distinguished. It might also be feasible to calculate how much the DME should affect the mean redshift of each image. Resolved observations of the source would be required to do this accurately. The DME is of order the source angular size divided by the Einstein radius times the redshift variation across the source. Thus, it mostly affects nearly edge-on spiral galaxies in certain orientations. This suggests that observers should reduce the DME by careful choice of target, a possibility we discuss in some detail.
dc.relation.ispartofMonthly Notices of the Royal Astronomical Societyen
dc.rights© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at
dc.subjectGravitational lensing: strongen
dc.subjectGalaxies: clusters: individual: 1E 0657-56en
dc.subjectGalaxies: kinematics and dynamicsen
dc.subjectDark matteren
dc.subjectQC Physicsen
dc.subjectQB Astronomyen
dc.titleEffects of lens motion and uneven magnification on image spectraen
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews.School of Physics and Astronomyen
dc.description.statusPeer revieweden

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