ROSEAU · Precision Cosmography with Strong Lensing Galaxy Clusters

Precision Cosmography with Strong Lensing Galaxy Clusters

A wide variety of cosmological probes allows us to measure the values of the cosmological parameters that define fundamental properties of the Universe, such as its age, size, its geometry, or its expansion rate. As cutting-edge experiments have become more precise, some discrepancy between the measurements of the expansion rate (defined by the Hubble constant) of the Universe from different methods has arisen, pointing to possible unknown biases or a call for new and interesting physics. In this context, the exploration of alternative and complementary techniques is crucial. Gravitational lensing occurs when the light rays from a background source are deflected by a galaxy or a galaxy cluster in the foreground, which acts as a lens. In the strong-lensing regime, multiple images of background sources are formed. The observed positions of these multiple images do not only depend on the total mass distribution of the foreground lens, but also on the underlying geometry of the Universe. In addition, if the luminosity of a multiply lensed source is intrinsically time varying, such as that of supernovae or quasars, the differences in light arrival times between the multiple images (or time delays) can be measured, enabling us to measure the expansion rate of the Universe. The main challenge associated with strong lensing cosmography relies on the fact that the characterisation of the cluster total mass distribution and the determination of the cosmological parameter values are closely intertwined. To exploit strong lensing galaxy clusters as high-precision cosmological probes, the total mass distribution of the lens clusters must be determined very accurately, driving this project to develop improved and accurate strong lensing models of galaxy clusters with a proper assessment of the leading sources of systematics. The ultimate goal of the project is to exploit these extraordinary lens systems to measure the cosmic expansion rate and geometry. This project is timely and strategically important given i) the current, intriguing tension in the measurements of the value of the cosmic expansion rate from different probes, and ii) the advent of large-volume, high-quality observations of lens galaxy clusters from state-of-the-art facilities. Developing new data analysis techniques will thus set a benchmark to exploit the exquisite, cutting-edge data from future facilities.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз