X‐Ray and Optical Flux Ratio Anomalies in Quadruply Lensed Quasars. I. Zooming in on Quasar Emission Regions

X-ray and optical observations of quadruply lensed quasars can provide amicroarcsecond probe of the lensed quasar, corresponding to scale sizes of\~10^2-10^4 gravitational radii of the central black hole. This high angularresolution is achieved by taking advantage of microlensing by stars in thelensing galaxy. In this paper we utilize X-ray observations of ten lensedquasars recorded with the Chandra X-ray Observatory as well as correspondingoptical data obtained with either the Hubble Space Telescope or ground-basedoptical telescopes. These are analyzed in a systematic and uniform way withemphasis on the flux-ratio anomalies that are found relative to the predictionsof smooth lens models. A comparison of the flux ratio anomalies between theX-ray and optical bands allows us to conclude that the optical emission regionsof the lensed quasars are typically larger than expected from basic thin diskmodels by factors of ~3-30.Comment: 11 pages, accepted to ApJ, expanded discussion of the analysis of the flux ratios and how they constrain the quasar emission region