Institute for Advanced Study/Princeton University Early Universe/Cosmology Lunch Discussion

Gravitational forces from the largest structures in the Universe leave a detectable imprint on galaxies and their local environment. This can manifest as the "Intrinsic Alignment" of galaxy orientations to the large-scale tidal field, although measuring these correlations is limited by the imaging of galaxy shapes and is not observed in blue or faint galaxies. I will present a new approach: tracing the tidal field with small groups of galaxies, or "multiplets". Multiplets mostly consist of 2-4 galaxies within 1 Mpc/h of each other, and we measure their orientations relative to the galaxy-traced tidal field. Using spectroscopic redshfits from the DESI Y1 survey, we detect intrinsic alignment out to projected separations of 100 Mpc/h and beyond redshift 1. We find a simillar signal regardless of galaxy luminosity or color, which could make multiplet alignment a useful tool for mapping the direction of the tidal field. Our detection demonstrates that galaxy clustering in the non-linear regime of structure formation preserves an interpretable memory of the large-scale tidal field.