Substructures in lens galaxies: PG1115+080 and B1555+375, two fold configurations |
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| Authors: | Marco Miranda Philippe Jetzer |
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| Institution: | (1) Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland |
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| Abstract: | We study the anomalous flux ratio which is observed in some four-image lens systems, where the source lies close to a fold
caustic. In this case two of the images are close to the critical curve and their flux ratio should be equal to unity, instead
in several cases the observed value differs significantly. The most plausible solution is to invoke the presence of substructures,
as for instance predicted by the Cold Dark Matter scenario, located near the two images. In particular, we analyze the two
fold lens systems PG1115+080 and B1555+375, for which there are not yet satisfactory models which explain the observed anomalous
flux ratios. We add to a smooth lens model, which reproduces well the positions of the images but not the anomalous fluxes,
one or two substructures described as singular isothermal spheres. For PG1115+080 we consider a smooth model with the influence
of the group of galaxies described by a SIS and a substructure with mass ∼105
M
⊙ as well as a smooth model with an external shear and one substructure with mass ∼108
M
⊙. For B1555+375 either a strong external shear or two substructures with mass ∼107
M
⊙ reproduce the data quite well. |
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| Keywords: | Cosmology: theory Dark matter Gravitational lensing Galaxies: haloes Substructures |
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