Related papers: Understanding micro-image configurations in quasar…
We present an analysis of seven strongly gravitationally lensed quasars and the corresponding constraints on the properties of dark matter. Our results are derived by modelling the lensed image positions and flux-ratios using a combination…
We present the results of microlens ray-tracing simulations showing the effect of absorbing material between a source quasar and a lensing galaxy in a gravitational lens system. We find that, in addition to brightness fluctuations due to…
I review the observations of gravitationally lensed quasars. These systems are important because they allow us to probe the properties of the lensing galaxies at various scales, and they also allow insights into the structures of the…
Spectral differences between lensed quasar image components are common. Since lensing is intrinsically achromatic, these differences are typically explained as the effect of either microlensing, or as light path time delays sampling…
We study the cosmological consequences of co-decaying dark matter - a recently proposed mechanism for depleting the density of dark matter through the decay of nearly degenerate particles. A generic prediction of this framework is an early…
In recent years, gravitational lensing has been used as a means to detect substructure in galaxy-sized halos, via anomalous flux ratios in quadruply-imaged lenses. In addition to causing anomalous flux ratios, substructure may also perturb…
Microlensing of gravitationally lensed quasars by the stars in the foreground lens galaxy can be used to probe the nature of dark matter, to determine the mean stellar mass in the lens galaxy, and to measure the internal structure of quasar…
The analysis of optical images of galaxy-galaxy strong gravitational lensing systems can provide important information about the distribution of dark matter at small scales. However, the modeling and statistical analysis of these images is…
The multiply imaged, gravitationally lensed quasar, QSO 2237+0305, has been the subject of recent optical monitoring campaigns, with its light curves displaying uncorrelated variability attributed to gravitational microlensing by masses in…
We investigate the statistics of flux anomalies in gravitationally lensed QSOs as a function of dark matter halo properties such as substructure content and halo ellipticity. We do this by creating a very large number of simulated lenses…
The Astrophysics of microquasars - galactic miniatures of the far distant quasars - has become one of the most active fields of modern Astronomy in recent years. Here I review the astronomical methods used for the investigation of these…
It has been revealed using microlensing that a considerable part, possibly more than half, of the dark matter in the halo of our Galaxy consists of objects with a mass spectrum ranging from 0.05 to 0.8 of the solar mass. What is the nature…
Gravitational microlensing is a powerful tool for probing the physical properties of quasar accretion disks and properties of the lens galaxy such as its dark matter fraction and mean stellar mass. Unfortunately the number of lensed quasars…
The cold dark matter scenario predicts that a large number of dark subhalos should be located within the halo of each Milky-way sized galaxy. One tell-tale signature of such dark subhalos could be additional milliarcsecond-scale image…
By monitoring $10^6$ quasars one could search for lensing by stars and Massive Compact Halo Objects (Machos) out to redshifts $z\sim 4$. If Machos have a present cosmological density $\Omega_{L,0}=1\%$, then the expected event rate is…
Gravitational lensing has emerged as a powerful probe of the matter distribution on subgalactic scales, which itself may contain important clues about the fundamental origins and properties of dark matter. Broadly speaking, two different…
Gravitational microlensing by the stellar population of lensing galaxies provides an important opportunity to spatially resolve the accretion disk structure in strongly lensed quasars. Some of the objects (like Einstein's cross) are…
Owing to the advent of large area photometric surveys, the possibility to use broad band photometric data, instead of spectra, to measure the size of the broad line region of active galactic nuclei, has raised a large interest. We describe…
Weak gravitational lensing of distant galaxies can probe the total projected mass distribution of foreground gravitational structures on all scales and has been used successfully to map the projected mass distribution of rich intermediate…
The dark halo substructures predicted by current cold dark matter simulations may in principle be detectable through strong-lensing image splitting of quasars on small angular scales (0.01 arcseconds or below). Here, we estimate the overall…