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Contribution of microlensing to X-ray variability of distant QSOs

Alexander F. Zakharov·Luka C. Popovic·Predrag Jovanovic
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Abstract

We consider a contribution of microlensing to the X-ray variability of high-redshifted QSOs. Cosmologically distributed gravitational microlenses could be localized in galaxies (or even in bulge or halo of gravitational macrolenses) or could be distributed in a uniform way. We have analyzed both cases of such distributions. We found that the optical depth for gravitational microlensing caused by cosmologically distributed deflectors could be significant and could reach $10^{-2} - 0.1$ at $z\sim 2$. This means that cosmologically distributed deflectors may contribute significantlly to the X-ray variability of high-redshifted QSOs ($z>2$). Considering that the upper limit of the optical depth ($τ\sim 0.1$) corresponds to the case where dark matter forms cosmologically distributed deflectors, observations of the X-ray variations of unlensed QSOs can be used for the estimation of the dark matter fraction of microlenses.

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Alexander F. Zakharov, Luka C. Popovic, Predrag Jovanovic. 2004-10-15. Contribution of microlensing to X-ray variability of distant QSOs. https://doi.org/10.1017/s1743921305002176

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