PAH mass fraction versus metallicity. Metallicity was derived from the FMR of Sanders et al. (2021). The robust and low-confidence q_PAH samples (Section 2.2) are shown with larger and smaller circles, respectively. We provide the values of the robust sample in Table 1. The z ∼ 0 data from Aniano et al. (2020) are shown in red. Following the analysis of Aniano et al. (2020), we fit both samples with a linear function, shown with solid lines (slopes of 3.63 ± 0.71 and 4.04 ± 0.51 and intercepts of −28.60 ± 6.14 and −31.94 ± 4.38 for the z ∼ 0 and 1.3 sample, respectively). The medians of the two samples below and above 12 + log(O/H) = 8.25 (dotted lines) are also shown. The two samples follow very similar trends. The average scatter in 12 + log(O/H) from FMR (0.05 dex, see text) and the strong-line metallicity calibration uncertainty for the z ∼ 0 sample (0.2 dex; Aniano et al. 2020) are shown in the bottom right. The error bars on the z ∼ 1.3 data are the metallicity measurement uncertainties from the SFR and mass uncertainties. The linear fits (solid lines) have slopes of 3.6 and 3.4 for the z ∼ 0 and 1.3 samples, respectively.