Mitigating intrinsic alignment impact on spectroscopic surveys

Abstract

Galaxy clustering statistics are an increasingly important observational probe of the large-scale structure of the Universe, especially because of their ability to constrain the growth rate through RSD effects. As a new generation of spectroscopic surveys is expected to bring a much higher degree of precision in our data, we will have to become more sensitive to potential sources of error in our analyses. Galaxy intrinsic alignment effects are typically neglected in galaxy clustering studies, but in recent years it has become apparent that such alignments are likely to contaminate our measurements of the growth rate through an orientation-dependent selection effect. In this thesis we investigate, using a Fisher forecast, how well this selection effect can be mitigated using intrinsic alignment statistics. Our results indicate that the selection effect is significant and that it cannot be resolved using the galaxy clustering power spectrum alone. However, we find that by adding intrinsic alignment statistics, most notably the galaxy-shape power spectrum, the effect can be mitigated effectively and we can still achieve good constraints on the growth rate. This implies that future studies aiming to constrain the growth rate through RSD measurements would benefit from a combined analysis of galaxy clustering and intrinsic alignment statistics.