Euclid Q1. Little red dots properties

We then excluded extended objects and possible line emitters and inspected the data visually to remove any imaging artefacts. The final selection included 3341 LRD candidates from z=0.33 to z=3.6, 29 of which were also detected in IRAC. The resulting rest-frame UV luminosity function, in contrast with previous JWST studies, shows that the number density of LRD candidates increases from high redshift to z=1.5-2.5 and decreases at even lower redshifts.

The subsample of more robust LRD candidates that are also detected with IRAC show a weaker evolution, however, which is affected by low statistics and limited by the IRAC resolution. The comparison with previous quasar UV luminosity functions shows that LRDs are not the dominant AGN population at z<4 and M_UV_<-21. Follow-up studies of these LRD candidates are pivotal to confirm their nature, probe their physical properties, and determine whether they are compatible with JWST sources because the different spatial resolution and wavelength coverage of Euclid and JWST might select different samples of compact sources.