Cross-correlation functions with individual molecular species for all four HR 8799 planets using the technique described in Section 4.2. For each planet’s spectrum (one planet per row), the S/Ns of the CCF are plotted for molecules templates using CO, H2O, CH4, and H2O+CO (one per column). The solid color line is the cross-correlation function of each molecular template with the data on the planet. The solid gray lines are the cross-correlation function of each template with extracted spectra that contained no planet signal. The vertical dashed line marks the approximate systemic radial velocity as calculated by Ruffio et al. (2019). HR 8799 c, d, and e have strong detections of CO and H2O individually, whereas HR 8799 b is only weakly detected when combining H2O and CO molecular templates.