Abstract
Changes of the magnification ratio of images in a lensed blazar, caused by microlensing on individual stars, have been proposed as a probe of the size and velocity of the emission region in the lensed source. We study whether similar changes in the magnification ratio can be caused by the microlensing on the intermediate size structures in the lensing galaxy, namely stellar clusters and giant molecular clouds. Our numerical simulations show that changes in the magnification ratio of two images with similar time scales (as seen in QSO B0218+357) can be obtained for relativistically-moving emission regions with sizes up to 0.01 pc in the case of microlensing on clumps in giant molecular clouds.
Highlights
A large mass located between a source of electromagnetic radiation and the observer will bend the trajectories of the photons and distort the observed image
Microlensing affects the images on much smaller angular scales, not observable with imaging instruments, but results in changes of the magnification that can be observed (e.g., [1]). As this effect is sensitive to small changes in the size and location of the emission region, it can be used to study the morphology of sources at unprecedented distance scales
We studied open clusters (OC), globular clusters (GC), and giant molecular clouds (GMC) as possible lenses during the 2012 high state of QSO B0218+357
Summary
A large mass located between a source of electromagnetic radiation and the observer will bend the trajectories of the photons and distort the observed image. These authors interpret the changes in the magnification ratio of the leading and trailing component as microlensing due to individual stars in the lensing galaxy Based on this, they put strong limits on the size of the emission region (.1014 –1015 cm) and the relative projected speed of the source and the lens, on the order of 103 km/s. We studied open clusters (OC), globular clusters (GC), and giant molecular clouds (GMC) as possible lenses during the 2012 high state of QSO B0218+357 The size of such objects would result in much larger regions in the source plane being magnified by a single microlensing event than for the case of individual stars. We summarize our findings recently published in [15]
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