A Study of Gravitational Lens Chromaticity using Ground-based Narrow Band Photometry

Ana M. Mosquera; José A. Muñoz; Evencio Mediavilla; Christopher S. Kochanek

doi:10.1088/0004-637X/728/2/145

paper

A Study of Gravitational Lens Chromaticity using Ground-based Narrow Band Photometry

arXiv:1008.3399 · doi:10.1088/0004-637X/728/2/145

Abstract

We present observations of wavelength-dependent flux ratios for four gravitational lens systems (SDSS~J1650+4251, HE~0435 $-$ 1223, FBQ 0951+2635, and Q~0142 $-$ 100) obtained with the Nordic Optical Telescope. The use of narrowband photometry, as well as the excellent seeing conditions during the observations, allows us to study their chromatic behavior. For SDSS~J1650+4251, we determine the extinction curve of the dust in the $z_{L} = 0.58$ lens galaxy and find that the 2175 Å\ feature is absent. In the case of HE~0435 $-$ 1223, we clearly detect chromatic microlensing. This allows us to estimate the wavelength-dependent size of the accretion disk. We find an R-band disk size of $r_{s}^{R} = 13 \pm 5$ light days for a linear prior on $r_{s}^{R}$ and $r_{s}^{R} = 7 \pm 6$ light days for a logarithmic prior. For a power-law size-wavelength scaling of $r_{s} \propto λ^{p}$ , we were able to constrain the value of the exponent to $p = 1.3 \pm 0.3$ for both $r_{s}^{R}$ priors, which is in agreement with the temperature profiles of simple thin disk models ( $p = 4/3$ ).

35 pages, 13 figures, and 6 tables. Matches accepted version, ApJ in press

A Study of Gravitational Lens Chromaticity using Ground-based Narrow Band Photometry

Abstract

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