New X-shaped bulge photometric model as a tool for measuring B/PS bulges and their X-structures in photometric studies

TL;DR

This paper introduces a new photometric model for boxy/peanut-shaped bulges that naturally includes X-structures, improving the accuracy of their measurement in both simulated and real galaxies.

Contribution

The paper develops a self-consistent photometric model incorporating X-structures in B/PS bulges, based on a spectral decomposition of a galaxy model, which aligns well with observations.

Findings

The new model accurately represents X-structures in B/PS bulges.

Systematic differences exist between previous and new measurement approaches.

Geometric parameters of X-structures are consistent across real and simulated galaxies using this model.

Abstract

Recent orbital studies of 3D bar structure in various numerical and analytical models show that X-structures that reside in boxy/peanut-shaped (B/PS) bulges are not delineated by some specific type of orbits, but are natural parts of them and formed by the same orbits that constitute such bulges. This implies that to accurately account for B/PS bulges and their X-structures in photometric studies, one needs the photometric model of B/PS bulge that includes an X-structure as its natural part. To find such a model, we considered a self-consistent numerical galaxy model where a typical B/PS bulge arises. Using spectral characteristics of particle-"stars", we decomposed the galaxy model onto the bar and non-bar components. We used the extracted 3D bar component to find an appropriate B/PS bulge photometric model, which can account for X-structures residing in such bulges. The resulted B/PS bulge photometric model has a truncated 2D Sersic profile with truncations introduced above (in the upper half-plane) and below (in the bottom half-plane) the rays of X-structures. We applied this model to represent B/PS bulges of various numerical models and some real galaxies. The comparison with previous works revealed that there are systematic shifts between the X-structure parameters of the same galaxies measured within the different approaches. We found that the geometric parameters of X-structures of real and modelled galaxies are consistent with each other if we measure them using our new model.