Systematic errors in weak gravitational lensing for cosmological investigations

Dr. Andres A. Plazas Malagon (host Cowsik), JPL/Caltech
September 28, 2017 at 3:00 pm
241 Compton
Event Description 

Gravitational lensing is the bending of light by any matter-energy distribution, inducing magnifications and distortions of background galaxies. As a direct consequence of general relativity, it has been identified as one the most powerful techniques to learn more about the dark matter distribution in galaxies and galaxy clusters, and on the largest scales of the universe. In turn, the study of the evolution of dark matter through cosmic history allows the placement of constraints on the dark energy that is causing the observed accelerated expansion of the universe. Both dark matter and dark energy add up to nearly 95% of the total contents of the universe, and their nature is largely unknown. Gravitational lensing is a fundamental tool in current and future projects, such as the Dark Energy Survey (DES), the Large Synoptic Survey Telescope (LSST), and NASA’s Wide Field Infrared Survey Telescope (WFIRST). However, the extraction of the gravitational lensing signal from astronomical measurements is a challenging process, and great attention must be placed on the understanding and characterization of systematic errors. In this talk I will discuss the sources of this type of errors in the regime of weak gravitational lensing (WL), and strategies to mitigate them. I will talk about the challenges of shape measurement in WL in the context of DES, LSST, and WFIRST. I will discuss the systematic errors originating from differential atmospheric refraction, and from the photon detectors used by those projects (charge-coupled devices and near-infrared detectors). I will conclude by presenting the recent cosmological results from the Dark Energy Survey year 1 data. These results pose the most stringent constraints to date on the dark energy equation of state and, for the first time, they enable a meaningful comparison between late and early universe, in particular with cosmological constraints from the Planck mission.

Coffee: 2:45 pm, 241 Compton