IRX (from SED fitting) plotted against M_star, SFR, and 12+log(O/H). In each panel, the individual best-fit regressions are shown by colored solid lines, and the gray regions denote the ±1σ interval around the mean regression. The left panel includes the “consensus” relation for galaxies at redshifts z ∼ 2 − 3 found by Bouwens et al. (2016), and shown as a green shaded region. As in Fig. 17, the right panel shows the PP04N2 calibration for 12+log(O/H) as described in the text. Also shown in the right panel is the correlation between IRX and O/H found for normal star-forming galaxies by Cortese et al. (2006) and for starbursts by Heckman et al. (1998); the region enclosed between these two relations is green-shaded, and is slightly steeper than the mean relation. As in previous figures, open symbols correspond to galaxies with low sSFR [Log(sSFR/yr⁻¹) ≤ −10.6], and filled symbols to high sSFR [Log(sSFR/yr⁻¹) > −10.6]. The three KINGFISH galaxies with IRX > 2 are NGC 1266 (IRX = 3.3), NGC 1482 (IRX = 2.8), and NGC 2146 (IRX = 2.6); the first two are early type S0’s and NGC 2146 is a luminous IR galaxy.