Left panel: velocity dispersion measurements for four massive quiescent galaxies at 3.2 < z < 3.7. Black solid line is the 1D galaxy spectrum, solid red line is the pPXF best-fit spectrum, and gray bars denote the 1σ uncertainty. Gray vertical bands indicate where there is either no flux determined or masked regions due to low sky transmission or emission line regions, and these have been masked in the pPXF fitting. Spectra are shown as observed flux, corrected for slit-loss as in Schreiber et al. (2018a). Vertical blue and orange dashed–dotted lines show absorption and emission line features from left to right: [O II], Hη, Hξ, Ca II H & K, Hδ, Hγ, Hβ, and [O III]. Right panel: H-band WFC3/F160W HST image stamps used in determining half-light radius re and other physical properties as in Table 2. Top right inset shows the residuals from our size modeling with the same pixel scale and stretch as the HST images.