Forward modelling of quasar light curves and the cosmological matter power spectrum on milliparsec scales

Understand

We devise an optimal method to measure the temporal power spectrum of the lensing and intrinsic fluctuations of multiply-imaged strongly lensed quasar light curves, along with the associated time delays.

• The method is based on a Monte-Carlo Markov Chain (MCMC) sampling of a putative gaussian likelihood, and accurately recovers the input properties of simulated light curves, as well as the "Time Delay Challenge".
• We apply this method to constrain the dimensionless cosmological (non-linear) matter power spectrum on milliparsec scales (comparable to the size of the solar system), to $\Delta_{\rm NL}^2< 4 \times 10^7$ at $k_{\rm NL} \sim 10^3 {\rm pc}^{-1}$.
• Using a semi-analytic nonlinear clustering model which is calibrated to simulations, the corresponding constraint on the primordial (linear) scalar power spectrum is ${\cal P}_{\cal R} < 3 \times 10^{-9}$ at $k_{\rm L}\sim$ 3 pc$^{-1}$.