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arXiv · 0808.3299

The Dark-Matter Fraction in the Elliptical Galaxy Lensing the Quasar PG1115+080

D. Pooley·S. Rappaport·J. Blackburne·P. L. Schechter·J. Schwab·J. Wambsganss
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Abstract

We determine the most likely dark-matter fraction in the elliptical galaxy quadruply lensing the quasar PG1115+080 based on analyses of the X-ray fluxes of the individual images in 2000 and 2008. Between the two epochs, the A2 image of PG1115+080 brightened relative to the other images by a factor of six in X-rays. We argue that the A2 image had been highly demagnified in 2000 by stellar microlensing in the intervening galaxy and has recently crossed a caustic, thereby creating a new pair of micro-images and brightening in the process. Over the same period, the A2 image has brightened by a factor of only 1.2 in the optical. The most likely ratio of smooth material (dark matter) to clumpy material (stars) in the lensing galaxy to explain the observations is ~90% of the matter in a smooth dark-matter component and ~10% in stars.

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D. Pooley, S. Rappaport, J. Blackburne, P. L. Schechter, J. Schwab, J. Wambsganss. 2008-08-25. The Dark-Matter Fraction in the Elliptical Galaxy Lensing the Quasar PG1115+080. https://doi.org/10.1088/0004-637x%2F697%2F2%2F1892

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