Distribution of sSFR as a function of stellar age for the low-mass central galaxies, represented by the number density of galaxies as indicated in the color bar (main panel). The horizontal dotted line shows the condition used to separate star-forming and quenched galaxies. The top and the right panels show the normalized density distributions of stellar age and sSFR, respectively, for the parent samples and sub-samples as indicated in the legends and described in Tables 1 and 2. The integral of each histogram sums to unity. The lines correspond to the median value for the PrimAll (solid) and PrimB (dashed) samples.