And Yet It Flips: Connecting Galactic Spin and the Cosmic
MNRAS 000,1–17 (2019) Preprint 5 June 2019 Compiled using MNRAS LATEX style file v3.0 And yet it flips: connecting galactic spin and the cosmic web Katarina Kraljic,1? Romeel Davé,1;2;3 and Christophe Pichon4;5 1 Institute for Astronomy, Royal Observatory, Edinburgh EH9 3HJ, United Kingdom 2 University of the Western Cape, Bellville, Cape Town 7535, South Africa 3 South African Astronomical Observatories, Observatory, Cape Town 7925, South Africa 4 Sorbonne Universités, UPMC Univ Paris 6 et CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France 5 Korea Institute for Advanced Study (KIAS), 85 Hoegiro, Dongdaemun-gu, Seoul, 02455, Republic of Korea Accepted XXX. Received YYY; in original form ZZZ ABSTRACT We study the spin alignment of galaxies and halos with respect to filaments and walls of the cosmic web, identified with DISPERSE, using the SIMBA simulation from z = 0 − 2. Massive halos’ spins are oriented perpendicularly to their closest filament’s axis and walls, while low mass halos tend to have their spins parallel to filaments and in the plane of walls. A simi- lar mass-dependent spin flip is found for galaxies, albeit with a weaker signal particularly at low mass and low-z, suggesting that galaxies’ spins retain memory of their larger-scale en- vironment. Low-z star-forming and rotation-dominated galaxies tend to have spins parallel to nearby filaments, while quiescent and dispersion-dominated galaxies show preferentially perpendicular orientation; the star formation trend can be fully explained by the stellar mass correlation, but the morphology trend cannot.
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