Main properties for our sample. In the left panel, we show that our sample (red diamonds) covers Hβ and [MgFe]′ values from B08 (grey circles). For comparison, we overplot the Hβ × [MgFe]′ grid measured from the E-MILES model library. Different ages are represented using different colours, and the different metallicities are all represented in black (from left to right, the [M/H] tracks are equal to −2.27, −1.79, −1.26, −0.66, −0.25, +0.15, and +0.40). In the right panels, we show the correlations between J − H colours (x-axis) and Hβ (upper), [MgFe]′ (middle), and H − K colours (bottom panels). We plot the respective errors in all panels as red crosses over each respective diamond.