Morphological coherence versus external environmental parameters. All open circles (representing sample clusters), all black error bars (being errors of the MD or ER) and red curves (indicating median filter lines) are the same as those in Fig. 7. (a) Distributions of the eccentricity, F_R, and F_z of the sample clusters with their MD. (b) Distributions of the eccentricity, F, and F of the sample clusters with their ER.