Applying MOG to lensing: Einstein rings, Abell 520 and the Bullet Cluster

We investigate gravitational lensing in the context of the MOG modified theory of gravity. Using a formulation of the theory with no adjustable or fitted parameters, we present the MOG equations of motion for slow, nonrelativistic test particles and for ultrarelativistic test particles, such as rays of light. We demonstrate how the MOG prediction for the bending of light can be applied to astronomical observations. Our investigation first focuses on a small set of strong lensing observations where the properties of the lensing objects are found to be consistent with the predictions of the theory. We also present an analysis of the colliding clusters 1E0657-558 (known also as the Bullet Cluster) and Abell 520; in both cases, the predictions of the MOG theory are in good agreement with observation.Comment: 14 pages, 2 figures; final proof before publicatio

Search for hidden turbulent gas through interstellar scintillation

Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected when the light of remote stars crosses a Galactic - disk or halo - refractive medium such as a molecular cloud. We present the promising results of a test performed with the ESO-NTT and the perspectives of detection.Comment: Structure and dynamics of disk galaxies, Petit Jean Mountain : United States (2013). arXiv admin note: substantial text overlap with arXiv:1208.637

Study of a Strategy for Parallax Microlensing Detection Towards the Magellanic Clouds

In this article, we have investigated the possibility to distinguish between different galactic models through the microlensing parallax studies. We show that a systematic search for parallax effects can be done using the currently running alert systems and complementary photometric telescopes, to distinguish between different lens distance distributions. We have considered two galactic dark compact objects distributions, with total optical depths corresponding to the EROS current upper limits. These models correspond to two extreme hypothesis on a three component galactic structure made of a thin disc, a thick disc, and a spherically symmetric halo. Our study shows that for sub-solar mass lenses, an exposure of $8\times 10^7$ star$\times$yr toward LMC should allow to distinguish between these two extreme models. In addition the self-lensing hypothesis (lensing by LMC objects) can efficiently be tested through the method proposed here.Comment: 10 pages, 12 eps figures. To be published in A&A (accepted version). Minor changes: - Discussion added on the differential velocity of the thick galactic disk with respect to the thin disk. - Quality and lisibility of figures improved. - Typo errors correcte

Search for Turbulent Gas through Interstellar Scintillation

Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected when the light of remote stars crosses a Galactic - disk or halo - refractive medium such as a molecular cloud.We present the promising results of a test performed with the ESO-NTT and the perspectives.Comment: Tenth Symposium on Sources and Detection of Dark Matter and Dark Energy in the Universe, Los-Angeles : \'Etats-Unis (2012