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تسجيل مستخدم جديدThe gravitational lens J1131-1231 - How to avoid missing an opportunity
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So far the lens J1131-1231 has been studied only at optical and X-ray wavelengths. A detection in the radio was almost missed as a result of an incorrect position and archive problems. A direct analysis of NVSS uv data - in contrast to the catalogue or images alone - provided sufficient evidence of a detection to justify further radio investigations. The system was subsequently observed with MERLIN and the EVN in e-VLBI mode. Even though MERLIN seems to show the lensed star-forming regions and the compact cores, a preliminary analysis of the EVN data only shows an AGN in the lens itself but not the lensed cores. Additional VLA observations will be carried out soon.
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We have observed the quadruply lensed quasar 1RXS J1131-1231 with the integral field spectrograph mode of the Kyoto Tridimensional Spectrograph II mounted on the Subaru telescope. Its field of view has covered simultaneously the three brighter lensed
images A, B, and C, which are known to exhibit anomalous flux ratios in their continuum emission. We have found that the [OIII] line flux ratios among these lensed images are consistent with those predicted by smooth-lens models. The absence of both microlensing and millilensing effects on this [OIII] narrow line region sets important limits on the mass of any substructures along the line of sight, which is expressed as M_E < 10^5 M_solar for the mass inside an Einstein radius. In contrast, the H_beta line emission, which originates from the broad line region, shows an anomaly in the flux ratio between images B and C, i.e., a factor two smaller C/B ratio than predicted by smooth-lens models. The ratio of A/B in the H_beta line is well reproduced. We show that the anomalous C/B ratio for the H_beta line is caused most likely by micro/milli-lensing of image C. This is because other effects, such as the differential dust extinction and/or arrival time difference between images B and C, or the simultaneous lensing of another pair of images A and B, are all unlikely. In addition, we have found that the broad H_beta line of image A shows a slight asymmetry in its profile compared with those in the other images, which suggests the presence of a small microlensing effect on this line emitting region of image A.
We present the main results of the first long-term spectrophotometric monitoring of the ``Einstein cross Q2237+0305 and of the single-epoch spectra of the lensed quasar J1131-1231. From October 2004 to December 2006, we find that two prominent micr
olensing events affect images A & B in Q2237+0305 while images C & D remain grossly unaffected by microlensing on a time scale of a few months. Microlensing in A & B goes with chromatic variations of the quasar continuum. We observe stronger micro-amplification in the blue than in the red part of the spectrum, as expected for continuum emission arising from a standard accretion disk. Microlensing induced variations of the CIII] emission are observed both in the integrated line intensity and profile. Finally, we also find that images C & D are about 0.1-0.3 mag redder than images A & B. The spectra of images A-B-C in J1131-1231 reveal that, in April 2003, microlensing was at work in images A and C. We find that microlensing de-amplifies the continuum emission and the Broad Line Region (BLR) in these images. Contrary to the case of Q2237+0305, we do not find evidence for chromatic microlensing of the continuum emission. On the other hand, we observe that the Balmer and MgII broad line profiles are deformed by microlensing. These deformations imply an anti-correlation between the width of the emission line and the size of the corresponding emitting region. Finally, the differential microlensing of the FeII emission suggests that the bulk of FeII is emitted in the outer parts of the BLR while another fraction of FeII is produced in a compact region.
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