Parameters of the secure ETG sample

We measure ETGs structural parameters and photometry from Hubble Space Telescope (HST) observations. We use high-quality spectroscopic data from the Multi Unit Spectroscopic Explorer (MUSE) to measure the galaxy central stellar velocity distribution and stellar population properties.

With these data, we construct the FP through a robust fitting procedure and analyze its tilt and scatter. We then introduce two hyperplane extensions, one including the stellar mass (M^*^-HP) and another including the stellar-over-total mass fraction (f_e_^*^-HP), and compare their coefficients and scatter to those of the FP. The FP of PLCK G287.0+32.9 is found to have best-fit parameter values consistent with those in the literature (alpha=1.2+/-0.1 and beta=-0.75+/-0.04), with an observed scatter of 0.088dex.