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Intrinsic Alignments (IA) are the main astrophysical contaminant in cosmic shear analyses and arise partly from correlations between galaxy shapes and the ellipticity of their host halos. However, halo shape measurements have yet to be incorporated into IA models. This SP will fill this gap by using halo shapes to inform a physically motivated halo model for IA.

Halo models analytically describe the matter distribution, assuming all matter and galaxies exist within dark matter halos. Despite simplifying assumptions, they can model, e.g., the matter power spectra (Mead et al., 2021) and higher‑order statistics (Linke et al., 2022). While IA halo models were proposed (Fortuna et al., 2021), they have not included the impact of halo shapes.

Mead A. J., Brieden S., Tröster T., Heymans C., 2021, MNRAS, 502, 1401, doi:10.1093/mnras/stab082

Linke L., Simon P., Schneider P., Farrow D. J., Rödiger J., Wright A. H., 2022, A&A, 665, A38, doi:10.1051/0004‑
6361/202243711

Fortuna M. C., Hoekstra H., Joachimi B., Johnston H., Chisari N. E., Georgiou C., Mahony C., 2021, MNRAS,
501, 2983, doi:10.1093/mnras/staa3802

Project Members

Lead: L. Linke

Other members: J. Krüger

Primary researchers involved: L. Linke, S. Ploeckinger, T. Schrabback, O. Hahn