Forward modelling of quasar light curves and the cosmological matter power spectrum on milliparsec scales
Abstract
We devise an optimal method to measure the temporal power spectrum of the lensing and intrinsic fluctuations of multiplyimaged strongly lensed quasar light curves, along with the associated time delays. The method is based on a MonteCarlo 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 (nonlinear) 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 semianalytic 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$^{1}$. This is the strongest constraint on primordial power spectrum at these scales, and is within an order of magnitude from the standard $\Lambda$CDM prediction. We also report measurements of temporal spectra for intrinsic variabilities of quasar light curves, which can be used to constrain the size of the emitting region in accretion disks. Future cadenced optical imaging surveys, such as LSST, should increase the number of observed strongly lensed quasars by 3 orders of magnitude and significantly improve these measurements, even though improvements in modelling quasar accretion and stellar microlensing are necessary.
 Publication:

arXiv eprints
 Pub Date:
 May 2018
 DOI:
 10.48550/arXiv.1805.06984
 arXiv:
 arXiv:1805.06984
 Bibcode:
 2018arXiv180506984K
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Instrumentation and Methods for Astrophysics;
 High Energy Physics  Phenomenology
 EPrint:
 Minor corrections to the text