Here's the proper link to the cartoon version!! 🧪🔭 cmlamman.github.io/doc/multiple...
Besides cosmology applications, overall I think this is just a neat result. We show that galaxy clustering in the non-linear regime of structure formation preserves an interpretable memory of the large-scale tidal field. *fin*
This compliments traditional 2-point clustering by retaining directional information imprinted by tidal forces, and contains additional LOS information compared to weak lensing. However, any applications will require some sort of calibration/understanding of the small effects!
We reproduce our measurements with AbacusSummit n-body simulations and come up with an analytic prediction. The scale-dependence of the signal traces the underlying tidal field and its amplitude is a result of small-scale (<1 Mpc) dynamics.
This is similar to the intrinsic alignment (IA) of individual galaxies, except: 1) does not rely on imaging 2) can be used to measure the IA blue galaxies. This has allowed us to measure alignment even with faint, blue ELGs which are beyond z=1 (shown in last plot).
Although multiplets are tiny by cosmologists' standards (~1 Mpc), their orientations are aligned with large-scale structure. Out to 150 Mpc/h! We detect a signal in all our galaxy samples: bright galaxies (BGS), luminous red galaxies (LRG) and emission-line galaxies (ELG).
Multiplets are close pairs, triplets, quads, etc. of galaxies that we identify with data from the DESI survey. We measure their orientations relative to the positions of other galaxies (this is similar to a squeezed 3-point correlation function).
We detect the alignment of galaxy multiplets: correlations between little groups of galaxies and the large-scale gravitational tidal field. We don't call them 'groups' in the paper because they're not necessarily virialized.
Today I am delighted to share a paper about a new way to measure the cosmic web🕸️ arxiv.org/abs/2408.11056cmlamman.github.io/doc/multipletI… For astronomers, I'll unravel it here with a short thread... /n
It was wonderful seeing my first REU student bring everything together, it was a fulfilling summer! Thank you Jonathan for running this awesome program 🌌
