Work

Classical Cepheids in the JWST and Roman era: A new theoretical framework and its metallicity dependence

Year: 2026

Type: article

Abstract: Context. Classical Cepheids are fundamental distance indicators that anchor the cosmic distance ladder through their period-luminosity, period-luminosity-color, and period-Wesenheit relations while also providing valuable constraints on the properties of young stellar populations. Recent advances in space-based near-infrared observations have highlighted the need for theoretical calibrations of classical Cepheid observables in modern photometric systems optimized for precision distance-scale applications. Aims. This work provides a homogeneous theoretical framework for classical Cepheids in the JWST/NIRCam and Roman/WFI photometric systems and explores its implications for their use as standard candles in the near-infrared regime. Methods. We exploited an extensive grid of nonlinear convective pulsation models transformed into the JWST/NIRCam and Roman/WFI systems. The models span a broad range of masses, effective temperatures, periods, metallicities, and assumptions on the efficiency of superadiabatic convection and on the adopted mass-luminosity relation. From these models, we derived mean magnitudes, colors, pulsation amplitudes, amplitude ratios, and new theoretical period-luminosity-color, period-Wesenheit, and metal-dependent period-Wesenheit relations. Results. We compared the theoretical Wesenheit relations with recent JWST observations of classical Cepheids in six SN Ia host galaxies from the SH0ES collaboration. We found excellent agreement between theoretical predictions and observations, with the largest systematic effects arising from the adopted mass-luminosity relation. The distance moduli derived from the theoretical relations are fully consistent with the empirical JWST determinations when a mildly overluminous mass-luminosity relation is adopted instead of the canonical one. Conclusions. These results establish a self-consistent pulsation-based calibration for JWST and Roman observations and provide a theoretical framework for future precision studies of the local distance scale.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202662111