Abstract
Abstract
We investigate the alignment of galaxy and halo orientations using the TNG300-1 hydrodynamical simulation. Our analysis reveals that the distribution of the 2D misalignment angle θ
2D can be well described by a truncated shifted exponential distribution with only one free parameter across different redshifts and galaxy/halo properties. We demonstrate that the galaxy–ellipticity (GI) correlations of galaxies can be reproduced by perturbing halo orientations with the obtained θ
2D distribution, with only a small bias (<3°) possibly arising from unaccounted for couplings between θ
2D and other factors. We find that both the 2D and 3D misalignment angles θ
2D and θ
3D decrease with ex situ stellar mass fraction F
acc, halo mass M
vir, and stellar mass M
*, while increasing with the disk-to-total stellar mass fraction F
disk and redshift. These dependences are in good agreement with our recent observational study based on BOSS galaxy samples. Our results suggest that F
acc is a key factor in determining galaxy–halo alignment. Grouping galaxies by F
acc nearly eliminates the dependence of θ
3D on M
vir for all three principle axes, and also reduces the redshift dependence. For θ
2D, we find a more significant redshift dependence than for θ
3D even after controlling F
acc, which may be attributed to the evolution of galaxy and halo shapes. Our findings present a valuable model for observational studies and enhance our understanding of galaxy–halo alignment.
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics