A Morphological and Statistical Analysis of Ansae in Barred Galaxies

TL;DR

This study statistically analyzes the occurrence and morphology of ansae in barred galaxies, revealing their prevalence in lenticulars and their correlation with bar strength, providing insights into their possible origin.

Contribution

It provides the first comprehensive statistical analysis of ansae frequency and morphology in barred galaxies using the de Vaucouleurs Atlas, highlighting their commonality and correlations.

Findings

Ansae are present in about 40% of SB0 galaxies.

The frequency of ansae decreases in later galaxy types.

Galaxies with ansae tend to have stronger bars.

Abstract

Many barred galaxies show a set of symmetric enhancements at the ends of the stellar bar, called {\it ansae}, or the ``handles'' of the bar. The ansa bars have been in the literature for some decades, but their origin has still not been specifically addressed, although, they could be related to the growth process of bars. But even though ansae have been known for a long time, no statistical analysis of their relative frequency of occurrence has been performed yet. Similarly, there has been no study of the varieties in morphology of ansae even though significant morphological variations are known to characterise the features. In this paper, we make a quantitative analysis of the occurrence of ansae in barred galaxies, making use of {\it The de Vaucouleurs Atlas of Galaxies} by Buta and coworkers. We find that $\sim 40%$ of SB0's show ansae in their bars, thus confirming that ansae are common features in barred lenticulars. The ansa frequency decreases dramatically with later types, and hardly any ansae are found in galaxies of type Sb or later. The bars in galaxies with ansae are stronger in the median than those in galaxies without ansae, but the presence of inner and outer rings is not related to the presence of ansae. Implications of these results and theories for the possible origin of ansae are discussed briefly.