We select a mass-complete sample of 225 quiescent galaxies at z>2 with M_* > 10^10\ M_ from PRIMER and JADES photometry spanning a total area of 320 sq. arcmin. We restrict our analysis to only area with optical coverage in three HST ACS filters, and provide evidence that this is important for selecting the most complete and clean samples of z>2 massive quiescent galaxy candidates. We investigate the contamination in our sample via JWST NIRSpec spectroscopic validation, Chandra X-ray imaging, and ALMA interferometry, calculating a modest total contamination fraction of 12. 9-₃. ₁^+4. 0 per cent. The removal of HST data increases star-forming galaxy contamination by 10 per cent and results in a 20 per cent loss of candidates recovered from HST+JWST data combined. We calculate massive quiescent galaxy number densities at 23, with discrepancies of up to 1 dex. We place 14 of our z>3 massive quiescent galaxies on the BPT and WHaN diagrams using medium-resolution spectroscopic data from the EXCELS survey. We find a very high incidence of faint AGN in our sample, at a level of 50 per cent, consistent with recent results at cosmic noon. This is interesting in the context of maintenance-mode feedback, which is invoked in many simulations to prevent quenched galaxies from re-igniting star formation. To properly characterise the evolution of early massive quiescent galaxies, greater coverage in optical filters and significantly larger spectroscopic samples will be required.
Stevenson et al. (Mon,) studied this question.