Total strength of the cross-correlation signal, as function of rest-frame velocity V_rest and planet projected orbital velocity K_P, for atmospheric models containing CO only (left panel), H₂O only (mid panel), and CH₄ only (right panel). It shows that carbon monoxide and water vapor are detected in the atmosphere of HD 179949 b around 2.3 μm, while methane is not. The signal-to-noise is computed by dividing the value of the cross correlation at each of the positions in the diagram by the standard deviation of the cross-correlation noise. Positive and negative cross-correlation signals are both plotted.