The Lens Galaxy in PG 1115+080 is an Ellipse

We use the structure of the Einstein ring image of the quasar host galaxy in the four-image quasar lens PG 1115+080 to determine the angular structure of the gravitational potential of the lens galaxy. We find that it is well described as an ellipsoid and that the best-fit nonellipsoidal models are...

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Bibliographic Details
Published in:The Astrophysical journal 2005-06, Vol.626 (1), p.51-57
Main Authors: Yoo, Jaiyul, Kochanek, Christopher S, Falco, Emilio E, McLeod, Brian A
Format: Article
Language:English
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Summary:We use the structure of the Einstein ring image of the quasar host galaxy in the four-image quasar lens PG 1115+080 to determine the angular structure of the gravitational potential of the lens galaxy. We find that it is well described as an ellipsoid and that the best-fit nonellipsoidal models are consistent with the ellipsoidal model. We find upper limits on the standard parameters for the deviation from an ellipse of parallel a super(B) sub(3)/a sub(0) parallel < 0.035 and parallel a super(B) sub(4)/a sub(0) parallel < 0.064. We also find that the position of the center of mass is consistent with the center of light, with an upper limit of parallel Delta super(x) parallel < 0".005 on the offset between them. Neither the ellipsoidal nor the nonellipsoidal models can reproduce the observed image flux ratios while simultaneously maintaining a reasonable fit to the Einstein ring, so the anomalous flux ratio of the A sub(1) and A sub(2) quasar images must be due to substructure in the gravitational potential such as compact satellite galaxies or stellar microlenses rather than odd angular structure in the lens galaxy.
ISSN:0004-637X
1538-4357
DOI:10.1086/429959