Ellipse-fitting in Mock Images of TNG50 Barred Galaxies

Abstract Recent studies have utilized the TNG50 simulation to explore barred galaxy morphology. The ellipse-fitting method is commonly used to assess properties of the isophotes in the central region of the disk. This work adapts the ellipse-fitting method to simulated images from TNG50, dealing with the issue of excessively pronounced ellipticities in central regions, whether in mass distribution maps or simulated radiative transfer images. To solve this problem, we introduce synthetic realism in the form of convolution with point spread functions, correcting the misbehavior in central ellipticities. These improvements simplify the application of ellipse-fitting to barred galaxies in the TNG50 simulation, enabling more accurate analysis of properties such as bar length and ellipticity, which would otherwise be more difficult to measure accurately. Thus, we conclude that when measuring shapes of simulated barred galaxies, one should apply realistic smoothing, otherwise the inner ellipticities will not be comparable to observations.