The cosmic evolution of boxy-peanut bulges : investigating the evolution in the frequency and mass transition of B/Ps at higher redshifts

Abstract

In the nearby Universe, the prevalence of barred disc galaxies with a stellar mass M⋆ > 1010M⊙ is characterised by the presence of vertically thickened bars that exhibit a boxy or peanut (B/P) shape when viewed edge-on. The formation of these B/P bulges is linked to violent vertical instabilities that arise in the bars, causing them to thicken and distort, eventually settling into the distinct B/P structure. This thesis investigated the evolution of the frequency of B/P bulges in barred galaxies at higher redshifts, from z = 0.2 to z = 1, using samples of ∼ 600 disc galaxies at each redshift. These galaxies were selected from the TNG50 cosmological suite with stellar masses M⋆ > 1010M⊙. The study discovered that the quantity of B/Ps rose from 21 in a sample at z = 1 to 75 at z = 0.2. The fraction of B/Ps in barred discs, fbp, increased from fbp ∼ 0.34 at z = 1 to fbp ∼ 0.41 at z = 0.2. At higher redshifts, the transition mass of B/Ps appeared to be consistent, and the threshold value for fbp remained approximately at M⋆ > 1010.2M⊙ across all redshifts. These findings align with a previous investigation by Kruk et al. (2019).