Detection of the Mass-Dependent Two-Fold Transition of Galaxy Spins in IllustrisTNG Simulations

Authors: Lee, Jounghun ; Moon, Jun-Sung ; Ryu, Suho ; Yoon, Suk-Jin

eprint arXiv:2105.06814

A numerical detection of the mass-dependent two-fold spin transition of the galaxies is presented. Analyzing a sample of the galaxies with stellar masses in the range of 109<(M⋆/M⊙)≤1011109<(M⋆/M⊙)≤1011 from the IllustrisTNG300-1 simulations, we explore the alignment tendency between the galaxy spins and the three eigenvectors of the linearly reconstructed tidal field as a function of M⋆M⋆ and its evolution over a broad range of redshift 0≤z≤2.50≤z≤2.5. Detecting a significant signal of the occurrence of the mass-dependent transition of the galaxy spins not only at z>1z>1 but also at z≤1z≤1, we show that the type of the galaxy spin transition varies with redshifts. As M⋆M⋆ increases beyond a certain threshold mass, the preferred directions of the galaxy spins transit from the third to the first tidal eigenvectors (type one) at z≤1z≤1 but from the third to the second tidal eigenvectors (type two) at z≥2z≥2, unlike those of the DM halos that undergo only the type two transitions at z≤1z≤1. It is also shown that both of the threshold mass and the transition type strongly depend on the galaxy status, morphology, star formation rate as well as on the environment. We suggest that the occurrence of the type two transition should be induced by the vorticity effect on the small mas scale, while the type one transition should be closely linked to some hydrodynamical mechanism which is effective most for the quiescent massive galaxies in the passive stage.

https://arxiv.org/abs/2105.06814