Cosmic stillness: High quiescent galaxy fractions across upper mass scales in the early Universe to z = 7 with JWST

Abstract

We present a detailed investigation into the abundance and morphology of high-redshift quenched galaxies at 3 < z < 7 using James Webb Space Telescope data in the NEP, CEERS, and JADES fields. Within these fields, we identify 90 candidate passive galaxies using specific star formation rates modelled with the BAGPIPES spectral energy distribution fitting code, which is more effective at identifying recently quenched systems than the classical UVJ method, which specializes in quenched objects > 1 Gyr. With this sample of galaxies, we find number densities broadly consistent with other works and a rapidly evolving passive fraction of high-mass galaxies (log 10 ( M· /M ·) > 9.5) in the range 3 < z < 5. We find that the fraction of galaxies with low star formation rates and mass 9.5 < 10.5 decreases from ∼25 per cent at 3 < z < 4 to ∼2 per cent at 5 < z < 7. Our passive sample of galaxies is shown to exhibit more compact light profiles compared to star-forming counterparts and some exhibit traces of active galactic nucleus activity through detections in either the X-ray or radio. At the highest redshifts ( z > 6 . 5) passive selections start to include examples of little red dots , which complicates any conclusions until their nature is better understood.