A Spitzer Study of Pseudobulges in S0 Galaxies : Secular Evolution of Disks

TL;DR

This study uses Spitzer mid-infrared imaging to analyze 185 S0 galaxies, identifying pseudobulges and revealing their distinct properties and correlations with disk parameters, shedding light on secular evolution processes.

Contribution

It provides a systematic analysis of pseudobulges in S0 galaxies using infrared data, highlighting their prevalence in fainter galaxies and their distinct disk characteristics compared to classical bulges.

Findings

Pseudobulges are more common in fainter S0 galaxies.

Disks in pseudobulge hosts have smaller scale lengths and fainter central brightness.

Distinct correlations between bulge and disk parameters depend on bulge type.

Abstract

In this Letter, we present a systematic study of lenticular (S0) galaxies based on mid-infrared imaging data on 185 objects taken using the Spitzer Infra Red Array Camera. We identify the S0s hosting pseudobulges based on the position of the bulge on the Kormendy diagram and the S\'{e}rsic index of the bulge. We find that pseudobulges preferentially occur in the fainter luminosity class (defined as having total K-band absolute magnitude M_K fainter than -22.66 in the AB system). We present relations between bulge and disk parameters obtained as a function of the bulge type. The disks in the pseudobulge hosting galaxies are found to have distinct trends on the r_e-r_d and \mu_d (0) - r_d correlations compared to those in galaxies with classical bulges. We show that the disks of pseudobulge hosts possess on average a smaller scale length and have a fainter central surface brightness than their counterparts occurring in classical bulge hosting galaxies. The differences found for discs in pseudobulge and classical bulge hosting galaxies may be a consequence of the different processes creating the central mass concentrations.