STRONG CHROMATIC MICROLENSING IN HE0047–1756 AND SDSS1155+6346

Abstract

We use spectra of the double lensed quasars HE0047-1756 and SDSS1155+6346 to\nstudy their unresolved structure through the impact of microlensing. There is\nno significant evidence of microlensing in the emission line profiles except\nfor the Ly$\\alpha$ line of SDSS1155+6346, which shows strong differences in the\nshapes for images A and B. However, the continuum of the B image spectrum in\nSDSS1155+6346 is strongly contaminated by the lens galaxy and these differences\nshould be considered with caution. Using the flux ratios of the emission lines\nfor image pairs as a baseline to remove macro-magnification and extinction, we\nhave detected strong chromatic microlensing in the continuum measured by\nCASTLES (http://www.cfa.harvard.edu/castles/), in both lens systems, with\namplitudes $0.09 (\\lambda 16000) \\lesssim |\\Delta m |\\lesssim 0.8 (\\lambda\n5439)$ for HE0047-1756, and $0.2 (\\lambda 16000) \\lesssim |\\Delta m |\\lesssim\n0.8 (\\lambda 5439)$ for SDSS1155+6346. Using magnification maps to simulate\nmicrolensing, and modeling the accretion disk as a Gaussian source (I $\\propto$\nexp(-R$^{2}$/2r$^2_s$)) of size r$_{s}$ $\\propto$ $ \\lambda^{p} $ we find,\nr$_{s}$ = 2.5$_{-1.4}^{+3.0}$ $\\sqrt{M/0.3M_{\\odot}}$ light days and p = 2.3\n$\\pm$ 0.8, at the rest frame for $\\lambda$ = 2045, for HE0047-1756 (log prior),\nand r$_{s}$ = 5.5$_{-3.3}^{+8.2}$ $\\sqrt{M/0.3M_{\\odot}}$ light days and p =\n1.5 $\\pm$ 0.6 at the rest frame of $\\lambda$ = 1398, for SDSS1155+6346 (log\nprior). Contrary to other studied lens systems, the chromaticity detected in\nHE0047-1756 and SDSS1155+6346 is large enough to fulfill the thin disk\nprediction. The inferred sizes, however, are very large compared to the\npredictions of this model, especially in the case of SDSS1155+6346.\n