Distributions in the H_δ − D_n4000 space of non-AGN galaxies (blue-shaded contours) and low (log[L_{X,2−10 keV}(erg s⁻¹)] < 43; orange circles) and high (43 < log[L_{X,2−10 keV}(erg s⁻¹)] < 44; red circles) L_X AGNs for different cosmic environments. Top panel: Distribution of isolated sources (field). Middle panel: distribution of sources associated with filaments. Bottom panel: distribution of sources found in the most dense fields. See text for more details.