SIMBAD references

We present a sample of 53 galaxy spectra at z_SPEC ∼ 5-12 from the JWST CEERS and RUBIES surveys, combining NIRSpec PRISM spectroscopy with NIRCam photometry. We aim to use these data to establish best practices for measuring the UV spectral slope (β) in the era of JWST. We adopt power-law fits to the rest-frame UV continuum from the spectroscopic data as our fiducial, or “true,” β values, and compare them to photometric estimates derived through three methods: (1) photometric power-law fitting, (2) power-law fitting to a spectral energy distribution (SED) model fitted to the photometry, (3) single-color fitting near the Lyman break, and (4) single-color fitting at fixed rest-frame wavelengths. We find that photometric power-law fitting and SED fitting are comparable and most closely recover the spectroscopic slopes, with minimal bias and scatter. Single-color estimates, while commonly used in past studies, show the most significant deviations and are not recommended when more than a single color is available. Our results highlight the limitations and strengths of each approach and provide practical guidance for measuring β from photometry when spectra are unavailable or are of insufficient quality.