BP/X-shaped bulge galaxies with GalaxyZoo/SDSS

Residual images are visually inspected to classify BP/X features into four categories: strong both-sided, both-sided, one-sided, and control (no BP/X). We also estimate stellar mass, distance, and physical size for each galaxy. Out of 6653 classified galaxies, we identified 1673 (~25%) with both-sided BP/X features-504 (~8%) strong and 1169 (~17%) weak-as well as 1112 (~17%) one-sided structures, making up a total of 2785 BP/X-hosting galaxies (~42%).

One-sided structures, likely signatures of ongoing buckling, are more frequent than strong both-sided bulges across all stellar masses. The fraction of BP/X bulges increases with stellar surface mass density, indicating a connection with bar formation in dense disks. We also find that galaxies with strong BP/X bulges contribute to increased scatter in the stellar mass-size and stellar mass-surface density relations, particularly at higher masses.