On the Detectability and Measurement of Galactic Bars as a Function of Redshift

The cosmic evolution of galactic bars offers key insights into the dynamical history of disk galaxies. However, studies of high-redshift bars are severely hampered by observational effects such as resolution degradation and surface brightness dimming. To quantify these biases and establish a robust methodology of bar detection and measurement for high-redshift galaxies, we develop an automated pipeline integrating isophotal ellipse fitting and Fourier decomposition. We benchmark its performance using a comprehensive set of mock observations generated by artificially redshifting high-quality images of local barred galaxies to match the background and resolution of HST (z about 0.5-3) and JWST (z about 1-6) observations. We find that applying standard bar detection criteria derived from local galaxies to high-redshift data results in a severe underestimation of the bar fraction, missing >50% of bars at z>0.5 in HST imaging and a similar fraction at z>2 in JWST imaging. Using adaptive, redshift-dependent criteria optimized via mock data achieves recovery rates above 60% out to z about 3 for HST and z about 6 for JWST. The ellipse fitting method significantly outperforms Fourier decomposition in measurement reliability. While ellipse fitting systematically underestimates bar length by about 4% -- 36% due to surface brightness dimming, this bias is consistent and correctable (σ about 0.88 -- 2.22); in contrast, the Fourier method is prone to catastrophic failures (σ about 2.40 -- 6.14) in the regime of low signal-to-noise ratio. We propose a standardized workflow that prioritizes mock-derived adaptive criteria and ellipse fitting, providing quantitative correction factors and empirical relations that enable future studies to recover intrinsic bar statistics from raw observations.