# Bar Fraction in Early- and Late-type Spirals

## TL;DR

This study compares different methods of classifying bars in spiral galaxies and examines how bar fractions vary with galaxy type, revealing that strong and weak bars have different formation processes and depend on host galaxy properties.

## Contribution

It provides a systematic comparison of visual, ellipse fitting, and Fourier analysis methods for bar classification and highlights the differing dependencies of strong and weak bars on galaxy types.

## Key findings

- Automatic methods detect strongly barred galaxies with 74-85% concordance.
- Different classification methods yield varying bar fractions (36-63%).
- Strong and weak bars show different dependencies on galaxy morphology.

## Abstract

Bar fractions depend on the properties of the host galaxies, which are closely related to the formation and evolution of bars. However, observational studies do not provide consistent results. We investigate the bar fraction and its dependence on the properties of the host galaxies by using three bar classification methods: visual inspection, ellipse fitting method, and Fourier analysis. Our volume-limited sample consists of 1,698 spiral galaxies brighter than $M_{\rm r}=-15.2$ with $z < 0.01$ from SDSS/DR7 visually classified by Ann et al. (2015). We first compare the consistency of classification among the three methods. Automatic classifications detect visually determined strongly barred galaxies with the concordance of $74\% \sim 85\%$. However, they have some difficulty in identifying bars, in particular, in bulge-dominated galaxies, which affects the distribution of bar fraction as a function of the Hubble type. We obtain, for the same sample, different bar fractions of 63%, 48%, and 36% by visual inspection, ellipse fitting, and Fourier analysis, respectively. The difference is mainly due to how many weak bars are included. Moreover, we find the different dependence of bar fraction on the Hubble type for strong versus weak bars: SBs are preponderant in early-type spirals whereas SABs in late-type spirals. This causes a contradictory dependence on host galaxy properties when different classification methods are used. We propose that strong bars and weak bars experience different processes for their formation, growth, and dissipation by interacting with different inner galactic structures of early-type and late-type spirals.