GPU-based shear–shear correlation calculation

Abstract

Light rays are deflected when travelling through a gravitational potential: this phenomenon is known as gravitational lensing. It causes the observed shapes of distant galaxies to be very slightly distorted by the intervening matter in the Universe, as their light travels towards us. This distortion is called cosmic shear. By measuring this component it is possible to derive the properties of the mass distribution causing the distortion. This in turn can lead to the measurement of the accelerated expansion of the Universe, as matter clumps together differently depending on its dynamics at each cosmological epoch. The measurement of the cosmic shear requires the statistical analysis of the ellipticities of millions of galaxies using very large astronomical surveys. In the past, due to the computational cost of the problem, this kind of analysis was performed by introducing simplifications in the estimation of such statistics. With the advent of scientific computing using graphics processing units, analysis of the shear can be addressed without approximations, even for very large surveys, while maintaining an affordable execution time. In this work, we present the creation and optimization of such a graphics processing unit code to compute the so-called shear–shear correlation function.