article published yes Zach Lewis author Michael V. Maseda author Anna De Graaff author Joel Leja author Bingjie Wang author Hans Walter Rix author Ian Mcconachie author Nikko J. Cleri author Rachel Bezanson author Leindert A. Boogaard author Gabriel Brammer author Jenny E. Greene author Michaela Hirschmann author Harley Katz author Ivo Labbé author Jorryt J Matthee author 7439a258-f3c0-11ec-9501-9df22fe067200000-0003-2871-127X Tim B. Miller author Rohan P. Naidu author Pascal A. Oesch author David J. Setton author Katherine A. Suess author Andrea Weibel author Katherine E. Whitaker author Christina C. Williams author JoMa department The correlation between galaxy stellar mass and gas-phase metallicity, known as the mass–metallicity relation (MZR), gives key insights into the processes that govern galaxy evolution. However, unquantified observational and selection biases can result in systematic errors in attempts to recover the intrinsic MZR, particularly at higher redshifts. We characterize the MZR at z ∼ 3–6 within a fully Bayesian framework using JWST/NIRSpec spectra of 191 galaxies from the RUBIES survey. We forward model the observed mass–metallicity surface using prospector-generated spectra to account for two selection biases: the survey selection function and the success in observing high signal-to-noise ratio emission lines. We demonstrate that the RUBIES selection function, based on F444W magnitude and F150W – F444W color, has a negligible effect on our measured MZR. A correct treatment of the non-Gaussian metallicity uncertainties from strong-line calibrations lowers the derived MZR normalization by 0.2 dex and flattens the slope by ∼20%; forward modeling the effect of emission line observability steepens the slope by ∼15%. Both of these biases must be taken into account in order to properly measure the intrinsic MZR. This novel forward-modeling process motivates careful consideration of selection functions in future surveys, and paves the way for robust, high-redshift chemical enrichment studies that trace the evolution of the MZR across cosmic time. https://research-explorer.ista.ac.at/download/22264/22273/2026_AstrophysicalJour_Lewis.pdf application/pdfno IOP Publishing2026 eng Galaxy evolutionChemical enrichmentMetallicityGalaxy abundancesScaling relations 0004-637X 1538-4357 2512.0313410.3847/1538-4357/ae7bfc 10052 Lewis Z, Maseda MV, De Graaff A, et al. The mass–metallicity relation and its observational effects at z ∼ 3–6. <i>The Astrophysical Journal</i>. 2026;1005(2). doi:<a href="https://doi.org/10.3847/1538-4357/ae7bfc">10.3847/1538-4357/ae7bfc</a> Lewis Z, Maseda MV, De Graaff A, Leja J, Wang B, Rix HW, Mcconachie I, Cleri NJ, Bezanson R, Boogaard LA, Brammer G, Greene JE, Hirschmann M, Katz H, Labbé I, Matthee JJ, Miller TB, Naidu RP, Oesch PA, Setton DJ, Suess KA, Weibel A, Whitaker KE, Williams CC. 2026. The mass–metallicity relation and its observational effects at z ∼ 3–6. The Astrophysical Journal. 1005(2), 159. Z. Lewis, M.V. Maseda, A. De Graaff, J. Leja, B. Wang, H.W. Rix, I. Mcconachie, N.J. Cleri, R. Bezanson, L.A. Boogaard, G. Brammer, J.E. Greene, M. Hirschmann, H. Katz, I. Labbé, J.J. Matthee, T.B. Miller, R.P. Naidu, P.A. Oesch, D.J. Setton, K.A. Suess, A. Weibel, K.E. Whitaker, C.C. Williams, The Astrophysical Journal 1005 (2026). Z. Lewis <i>et al.</i>, “The mass–metallicity relation and its observational effects at z ∼ 3–6,” <i>The Astrophysical Journal</i>, vol. 1005, no. 2. IOP Publishing, 2026. Lewis, Zach, et al. “The Mass–Metallicity Relation and Its Observational Effects at z ∼ 3–6.” <i>The Astrophysical Journal</i>, vol. 1005, no. 2, 159, IOP Publishing, 2026, doi:<a href="https://doi.org/10.3847/1538-4357/ae7bfc">10.3847/1538-4357/ae7bfc</a>. Lewis, Z., Maseda, M. V., De Graaff, A., Leja, J., Wang, B., Rix, H. W., … Williams, C. C. (2026). The mass–metallicity relation and its observational effects at z ∼ 3–6. <i>The Astrophysical Journal</i>. IOP Publishing. <a href="https://doi.org/10.3847/1538-4357/ae7bfc">https://doi.org/10.3847/1538-4357/ae7bfc</a> Lewis, Zach, Michael V. Maseda, Anna De Graaff, Joel Leja, Bingjie Wang, Hans Walter Rix, Ian Mcconachie, et al. “The Mass–Metallicity Relation and Its Observational Effects at z ∼ 3–6.” <i>The Astrophysical Journal</i>. IOP Publishing, 2026. <a href="https://doi.org/10.3847/1538-4357/ae7bfc">https://doi.org/10.3847/1538-4357/ae7bfc</a>. 222642026-07-12T22:02:17Z2026-07-13T07:40:41Z