We investigate the emission of active galactic nucleus (AGN) dusty tori in infrared domain. Following theoretical predictions derived from hydrodynamical simulations, we model the dusty torus as a 3D two-phase medium with high-density clumps and low-density medium filling the space between the clumps. Spectral energy distributions (SEDs) and images of the torus at different wavelengths are obtained using the 3D Monte Carlo radiative transfer code SKIRT. Our approach of generating clumpy structure allows us to model the tori with single clumps, complex structures of merged clumps or interconnected sponge-like structure. A corresponding set of clumps-only models and models with smooth dust distribution is calculated for comparison. We found that dust distribution, optical depth, clump size and their actual arrangement in the innermost region all have an impact on the shape of near-and mid-infrared SED. The 10-µm silicate feature can be suppressed for some parameters, but models with smooth dust distribution are also able to produce a wide range of silicate feature strength. Finally, we find that having the dust distributed in a two-phase medium might offer a natural solution to the lack of emission in near-infrared, compared to observed data, which affects clumpy models currently available in the literature.

Abstract.We report the discovery of a new quadruply imaged quasar surrounded by an optical Einstein ring candidate. Spectra of the different components of 1RXS J113155.4−123155 reveal a source at z = 0.658. Up to now, this object is the closest known gravitationally lensed quasar. The lensing galaxy is clearly detected. Its redshift is measured to be z = 0.295. Additionally, the total V magnitude of the system has varied by 0.3 mag between two epochs separated by 33 weeks. The measured relative astrometry of the lensed images is best fitted with an SIS model plus shear. This modeling suggests very high magnification of the source (up to 50 for the total magnification) and predicts flux ratios between the lensed images significantly different from what is actually observed. This suggests that the lensed images may be affected by a combination of micro or milli-lensing and dust extinction effects.

Abstract. We present the results of two-band CCD photometric monitoring of the gravitationally lensed quasar Q 0142−100 (UM 673). The data, obtained at ESO-La Silla with the 1.54 m Danish telescope in the Gunn i-band (October 1998−September 1999) and in the Johnson V-band (October 1998 to December 2001), were analyzed using three different photometric methods. The light-curves obtained with all methods show variations, with a peak-to-peak amplitude of 0.14 mag in V. Although it was not possible to measure the time delay between the two lensed QSO images, the brighter component displays possible evidence for microlensing: it becomes bluer as it gets brighter, as expected under the assumption of differential magnification of a quasar accretion disk.