Photometric characterization of a well defined sample of isolated galaxies in the context of the AMIGA project

TL;DR

This study conducts a detailed photometric analysis of isolated spiral galaxies, revealing that most host pseudobulges likely formed through internal processes, with isolated galaxies showing distinct structural properties compared to non-isolated ones.

Contribution

It provides new insights into the structural properties and bulge types of isolated galaxies, emphasizing the role of secular evolution and bars in pseudobulge formation.

Findings

Most late-type isolated disk galaxies host pseudobulges.

Isolated galaxies tend to have larger bars and are more symmetric.

Distinct differences between Sb and Sbc-Sc types in various properties.

Abstract

We perform a detailed photometric analysis (bulge-disk-bar decomposition and Concentration-Asymmetry-Clumpiness - CAS parametrization) for a well defined sample of isolated galaxies, extracted from the Catalog of Isolated Galaxies (Karachentseva 1973) and reevaluated morphologically in the context of the AMIGA project. We focus on Sb-Sc morphological types, as they are the most representative population among the isolated spiral galaxies. Assuming that the bulge Sersic index and/or Bulge/Total luminosity ratios are reasonable diagnostics for pseudo- versus classical bulges, we conclude that the majority of late-type isolated disk galaxies likely host pseudobulges rather than classical bulges. Our parametrization of galactic bulges and disks suggests that the properties of the pseudobulges are strongly connected to those of the disks. This may indicate that pseudobulges are formed through internal processes within the disks (i.e. secular evolution) and that bars may play an important role in their formation. Although the sample under investigation covers a narrow morphological range, a clear separation between Sb and Sbc-Sc types is observed in various measures, e.g. the former are redder, brighter, have larger disks and larger bars, more luminous bulges, are more concentrated, more symmetric and clumpier than the latter. A comparison with samples of spiral galaxies (within the same morphological range) selected without isolation criteria reveals that the isolated galaxies tend to host larger bars, are more symmetric, less concentrated and less clumpy.