The Coexistence of Classical Bulges and Disky Pseudobulges in Early-Type Disk Galaxies

TL;DR

This paper reveals that early-type disk galaxies can host both classical bulges and disky pseudobulges simultaneously, challenging the idea that these structures are mutually exclusive and suggesting a more complex galaxy formation history.

Contribution

It demonstrates that classical bulges and disky pseudobulges can coexist in the same galaxy, providing new insights into galaxy structure and formation processes.

Findings

Galaxies can contain both classical bulges and disky pseudobulges.

Pseudobulges are not solely formed by secular evolution.

Classical bulges are likely formed by rapid mergers.

Abstract

Close examination of so-called "pseudobulges" in several early-type disk galaxies indicates that they are actually composite structures consisting of both a flattened, kinematically cool disklike structure ("disky pseudobulge") and a rounder, kinematically hot spheroidal structure ("classical bulge"). This indicates that pseudobulges, thought to form from internal secular evolution, and classical bulges, thought to form from rapid mergers, are not exclusive phenomena: some galaxies can have both.