Spiral Galaxies as Progenitors of Pseudobulge Hosting S0s

TL;DR

This study uses infrared imaging to analyze the structural properties of pseudobulges in S0 and spiral galaxies, revealing their prevalence and potential evolutionary pathways from spirals to S0s through secular processes and gas stripping.

Contribution

It provides a detailed analysis of pseudobulge fractions in S0 and spiral galaxies using infrared data and bulge-disk decomposition, highlighting secular evolution as a key process.

Findings

25 S0s (14%) and 24 spirals (77%) host pseudobulges.

Pseudobulge hosting spirals can evolve into S0s via gas stripping.

Bulge effective radius correlates with disk scale length for pseudobulges.

Abstract

We present observations of pseudobulges in S0 and spiral galaxies using imaging data taken with the Spitzer Infra-Red Array Camera. We have used 2-d bulge-disk-bar decomposition to determine structural parameters of 185 S0 galaxies and 31 nearby spiral galaxies. Using the Sersic index and the position on the Kormendy diagram to classify their bulges as either classical or pseudo, we find that 25 S0s (14%) and 24 spirals (77%) host pseudoblges. The fraction of pseudobulges we find in spiral galaxies is consistent with previous results obtained with optical data and show that the evolution of a large fraction of spirals is governed by secular processes rather than by major mergers. We find that the bulge effective radius is correlated with the disk scale length for pseudobulges of S0s and spirals, as expected for secular formation of bulges from disk instabilities, though the disks in S0s are significantly smaller than those in spirals. We show that early-type pseudobulge hosting spirals can transform to pseudobulge hosting S0s by simple gas stripping. However, simple gas stripping mechanism is not sufficient to transform the late-type pseudobulge hosting spirals into pseudobulge hosting S0s.