Figure 4.

Result of a singular value decomposition of the laser-off data matrix highlighted by the black rectangle in figure 1. Panel (a) shows the seven first left-singular vectors U_i multiplied by their corresponding singular value, U_i,i. Panel (b) shows the seven corresponding right-singular vectors, i.e. the seven first columns of V. Panel (c) shows, from top to bottom, the magnitude of the singular values as a function of column number i as well as the autocorrelation functions of U_i and V_i. The magnitudes of S_i,i indicate two dominant contributions to this subset of the data, but no cut-off is evident from R(U_i) or R(V_i). (Online version in colour.)