Galaxies of Euclid (Q1)

Using spectroscopic information from DESI, we perform broad-line and narrow-line AGN selections, yielding 4392 AGN candidates across the Q1 fields. We investigate and refine the Euclid Q1 probabilistic random forest QSO population, selecting a refined sample of 180666 candidates. Additionally, we perform SED fitting on sources with available z_spec_ and, utilizing the derived AGN fraction, identify 7766 AGN candidates.

To improve selection purity, we define two new colour criteria (JH_IeY and IeH_gz), finding 313714 and 267513 candidates, respectively, across the Q1 fields. We find a total of 229779 AGN candidates equivalent to an AGN surface density of 3641 deg^{-2} for 18<Ie<=24.5, and a subsample of 30422 candidates corresponding to an AGN surface density of 482 deg^{-2} when limiting the depth to 18<Ie<=22. The AGN surface densities recove