# The Frequency and Stellar-Mass Dependence of Boxy/Peanut-Shaped Bulges in Barred Galaxies

## TL;DR

This study reveals that the occurrence of boxy/peanut-shaped bulges in barred galaxies strongly depends on stellar mass, with higher mass galaxies exhibiting a significantly greater frequency of these bulges, independent of gas content.

## Contribution

It provides the first comprehensive analysis of the stellar-mass dependence of B/P bulges in a local galaxy sample, clarifying their relation to galaxy parameters and bar properties.

## Key findings

- 79% of high-mass galaxies have B/P bulges
- Only 12% of low-mass galaxies have B/P bulges
- No significant effect of atomic gas mass ratio on B/P bulge presence

## Abstract

From a sample of 84 local barred, moderately inclined disc galaxies, we determine the fraction which host boxy or peanut-shaped (B/P) bulges (the vertically thickened inner parts of bars). We find that the frequency of B/P bulges in barred galaxies is a very strong function of stellar mass: 79% of the bars in galaxies with log (M_{star}/M_{sun}) >~ 10.4 have B/P bulges, while only 12% of those in lower-mass galaxies do. (We find a similar dependence in data published by Yoshino & Yamauchi 2015 for edge-on galaxies.) There are also strong trends with other galaxy parameters -- e.g., Hubble type: 77% of S0-Sbc bars, but only 15% of Sc-Sd bars, have B/P bulges -- but these appear to be side effects of the correlations of these parameters with stellar mass. In particular, despite indications from models that a high gas content can suppress bar buckling, we find no evidence that the (atomic) gas mass ratio M_{atomic}/M_{star} affects the presence of B/P bulges, once the stellar-mass dependence is controlled for. The semi-major axes of B/P bulges range from one-quarter to three-quarters of the full bar size, with a mean of R_{box}/L_{bar} = 0.42 +/- 0.09 and R_{box}/a_{max} = 0.53 +/- 0.12 (where R_{box} is the size of the B/P bulge and a_{max} and L_{bar} are lower and upper limits on the size of the bar).