Stellar populations of classical and pseudo-bulges for a sample of isolated spiral galaxies

TL;DR

This study analyzes the stellar populations of bulges in isolated spiral galaxies, revealing that both pseudo- and classical bulges are mainly old, with subtle differences in age and dynamics, highlighting the role of secular evolution.

Contribution

It provides a comparative analysis of stellar populations in pseudo- and classical bulges within isolated galaxies using spectroscopic data and synthesis modeling.

Findings

Both bulge types are predominantly old (~10 Gyr).

Pseudo-bulges show slightly younger ages but are hard to distinguish based on stellar populations.

Pseudo-bulges have lower stellar velocity dispersion, indicating different dynamical support.

Abstract

In this paper we present the stellar population synthesis results for a sample of 75 bulges in isolated spiral Sb-Sc galaxies, using the spectroscopic data from the Sloan Digital Sky Survey and the STARLIGHT code. We find that both pseudo-bulges and classical bulges in our sample are predominantly composed of old stellar populations, with mean mass-weighted stellar age around 10 Gyr. While the stellar population of pseudo-bulges is, in general, younger than that of classical bulges, the difference is not significant, which indicates that it is hard to distinguish pseudo-bulges from classical bulges, at least for these isolated galaxies, only based on their stellar populations. Pseudo-bulges have star formation activities with relatively longer timescale than classical bulges, indicating that secular evolution is more important in this kind of systems. Our results also show that pseudo-bulges have a lower stellar velocity dispersion than their classical counterparts, which suggests that classical bulges are more dispersion-supported than pseudo-bulges.