Influence of Barlens on the Bulge Parameters in the 2D Image Decomposition

TL;DR

This study investigates how including the barlens component in 2D image decomposition affects the accuracy of bulge parameter measurements in barred galaxies, emphasizing the importance of proper modeling to avoid overestimations.

Contribution

The paper demonstrates the impact of barlens modeling on bulge parameter accuracy and proposes an optimal method for including barlens in 2D decomposition.

Findings

Ignoring barlens can overestimate bulge-to-total ratio by 50%

Including barlens reduces B/T by approximately 30-50%

Projection effects increase uncertainties at higher inclinations

Abstract

Recent observations and simulations have shown that a buckled bar in the face-on view can be considered as a combination of a long flat bar and a short round barlens (corresponding to the boxy/peanut bulge in the edge-on view). However, the barlens component can be misidentified as the bulge, potentially leading to inaccurate bulge parameter measurements in two-dimensional (2D) image decomposition. Our goal is to explore the optimal method for modeling the barlens component and to understand its impact on bulge parameter measurements in 2D image decomposition. We first analyze mock images from two different simulations (with/without bulge) to verify our decomposition method. We then apply the method to two nearby barred galaxies, NGC 1533 and NGC 7329, from the Carnegie-Irvine Galaxy Survey (CGS). Using GALFIT, we conduct 2D image decomposition by gradually increasing the complexity of model configurations. We also explore the effects of inclination by projecting the simulated galaxy to various viewing angles and analyzing the variations in bulge and barlens parameters. From the mock images, we find that the bulge-to-total ratio (B/T) could be overestimated by 50$\%$ without considering the barlens component; the S\'ersic index and effective radius of the bulge are also affected to varying degrees. The decomposition results of the two CGS galaxies are consistent with our mock image tests. Uncertainties of the structural parameters of the bulge and barlens are larger at higher inclination angels due to the strong projection effect in the central region. Our findings underscore the necessity of accurately modeling the barlens, revealing that its inclusion in 2D image decomposition can lead to a decrease in B/T by $\sim$30-50$\%$, with other bulge parameters, such as the S\'ersic index and effective radius, also affected.