The robustness in identifying and quantifying high-redshift bars using JWST observations

¹ Department of Astronomy, Xiamen University, Xiamen, Fujian 361005, PR China
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: phyyueyu@gmail.com
³ Kavli Institute for the Physics and Mathematics of the Universe (WPI),The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
e-mail: si-yue.yu@ipmu.jp
⁴ The Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, PR China
⁵ Department of Astronomy, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, PR China

Received: 9 November 2023
Accepted: 17 May 2024

Abstract

Understanding the methodological reliability in identifying and quantifying high-redshift bars is essential for studying their evolution with the James Webb Space Telescope (JWST). We used nearby spiral galaxies to generate simulated images at various resolutions and signal-to-noise ratios, and obtained the simulated galaxy images observed in the Cosmic Evolution Early Release Science (CEERS) survey. Through a comparison of measurements before and after image degradation, we show that the bar measurements for massive galaxies remain robust against noise. While the measurement of the bar position angle remains unaffected by resolution, the measured bar ellipticity is significantly underestimated in low-resolution images. The size measurement is barely affected on average as long as the intrinsic bar size a_{bar,  true} > 2 × FWHM. To address these effects, correction functions are derived. We also find that bar detections remain effective at ∼100% when the a_{bar,  true}/FWHM is above 2, below which the rate drops sharply, quantitatively validating the effectiveness of using a_{bar,  true} > 2 × FWHM as a bar detection threshold. We analyzed a set of simulated CEERS images and took into account observational effects and plausible galaxy (and bar-size) evolution models. We show that a significant (and misleading) reduction in the detected bar fraction with increasing redshift would apparently result even if the true bar fraction remained constant. Our results underscore the importance of disentangling the true bar fraction evolution from resolution effects and bar size growth.