How do galaxies build up their spin in the cosmic web?

TL;DR

This study uses the Horizon-AGN simulation to reveal how galaxy spin orientations depend on mass and morphology, showing alignment with cosmic filaments for low-mass galaxies and perpendicular orientation for high-mass ones, influenced by mergers and accretion.

Contribution

It provides a detailed analysis of the physical mechanisms behind galaxy spin orientation trends within the cosmic web, highlighting the roles of mergers and accretion.

Findings

Low-mass galaxies align with filaments

High-mass galaxies tend to be perpendicular to filaments

Mergers and accretion significantly influence spin orientation

Abstract

Using the Horizon-AGN simulation we find a mass dependent spin orientation trend for galaxies: the spin of low-mass, rotation-dominated, blue, star-forming galaxies are preferentially aligned with their closest filament, whereas high-mass, velocity dispersion- supported, red quiescent galaxies tend to possess a spin perpendicular to these filaments. We explore the physical mechanisms driving galactic spin swings and quantify how much mergers and smooth accretion re-orient them relative to their host filaments and impact their shape. In particular, we analyze the effect of dispersion and morphology of galaxies and discuss potential tracers for prospective surveys.