Simulating intergalactic quasar scintillation
Intergalactic scintillation of distant quasars is sensitive to free electrons and therefore complements Ly absorption line experiments probing the neutral intergalactic medium (IGM). We present a new scheme to compute IGM refractive scintillation effects on distant sources in combination with Adaptive Mesh Renement cosmological simulations. First we validate our model by reproducing the well-known interstellar scintillation (ISS) of Galactic sources. The simulated cosmic density eld is then used to infer the statistical properties of intergalactic scintillation. Contrary to previous claims, we nd that the scattering measure of the simulated IGM at z 30 GHz the IGM contribution dominates over ISS modulation. We compare our model with data from a 0:3 6 z 6 2 quasar sample observed at obs = 8:4 GHz. For this high frequency (10:92 6 s 6 25:2), high galactic latitude sample ISS is negligible, and IGM scintillation can reproduce the observed modulation with a 4% accuracy, without invoking intrinsic source variability. We conclude by discussing the possibility of using IGM scintillation as a tool to pinpoint the presence of intervening high-z groups/clusters along the line of sight, thus making it a probe suitably complementing Sunyaev-Zeldovich data recently obtained by Planck.