Dependence of the three spectral features detailed in Sect. 3.2 (from top to bottom: [OII] EW, Hδ EWs, and D_n4000) as a function of stellar mass (left), over-density (middle), and SED-derived SFR (right). We show our stellar mass representativeness limit as a vertical dotted line in the left panels and show as empty symbols the measurements for which the completeness effects are large. We note that for bins that are not defined in stellar mass (middle and right panels), the composite spectra are built from galaxies with stellar mass greater than 10¹⁰ M_⊙. Results from this paper are shown as large symbols connected by a dotted line with associated error bars derived from the 16th and 84th percentiles of the 1000 bootstrapped fits (when the error bars are not shown, it implies an error smaller than the symbol size). The trends with stellar mass show a decrease in [OII] and Hδ emission (blue squares) and absorption (red circles) strength and an increase in the average age of the stellar population (traced by D_n4000). The trends with over-density show a peak in [OII] EW at filament-like densities, and Hδ EWs show little dependence on local density. There is also a clear trend that galaxies are older in higher density regions. Lastly, the strength of [OII] and Hδ increases with SFR (except for the most strongly star-forming galaxies), and younger populations lie in galaxies with higher SFR, as expected. We compare our results to other surveys in the literature (Bridge et al. 2015; Darvish et al. 2015a; Cava et al. 2015; Wu et al. 2018; Hernán-Caballero et al. 2013; Vergani et al. 2008; Muzzin et al. 2012). For a more detailed discussion of the differences, we refer to Sects. 4.2.1 and 4.2.2.