Cosmological pseudobulge formation

TL;DR

This paper demonstrates through cosmological simulations that pseudobulges in Milky Way-sized galaxies form mainly from early rapid gas supply before disk formation, challenging the traditional view of secular evolution as their primary formation channel.

Contribution

It reveals that pseudobulges form predominantly before disk formation via rapid gas inflow, contrasting with the secular evolution model.

Findings

Pseudobulges form mostly before disk formation.

Main formation channel is rapid gas supply at high redshift.

Progenitors observed as high-redshift disks.

Abstract

Bulges can be classified into classical and pseudobulges; the former are considered to be end products of galactic mergers and the latter to form via secular evolution of galactic disks. Observationally, bulges of disk galaxies are mostly pseudobulges, including the Milky Way's. We here show, by using self-consistent cosmological simulations of galaxy formation, that the formation of pseudobulges of Milky Way-sized disk galaxies has mostly completed before disk formation; thus the main channel of pseudobulge formation is not secular evolution of disks. Our pseudobulges form by rapid gas supply at high-redshift and their progenitors would be observed as high-redshift disks.