4MOST ChANGES: Catalog of high-redshift quasar candidates (4.5 < z < 7) selected via spectral-energy-distribution fitting

The identification of high-redshift quasars (z > 4.5) is critical for studying the early Universe, supermassive-black-hole growth, and cosmic reionization. Most known high-redshift quasars are located in the northern hemisphere, leaving the southern sky largely unexplored. As part of the 4-meter Multi-Object Spectroscopic Telescope (4MOST) and Chilean AGN/Galaxy Extragalactic Survey (ChANGES) S1604 survey, we aim to create a large catalog of high-redshift quasar candidates in the southern hemisphere using multiwavelength photometry and spectral-energy-distribution (SED) fitting, with the goal of spectroscopic follow-up with 4MOST. We constructed a multiband photometric catalog by combining optical data from the Dark Energy Camera Local Volume Exploration Survey (DELVE DR2) and Dark Energy Camera Legacy Survey (DECaLS DR10), near-infrared data from the VISTA Hemisphere Survey (VHS DR5) with an additional field of the VISTA Kilo-degree Infrared Galaxy Public Survey (VIKING), mid-infrared data from the Wide-field Infrared Survey Explorer (AllWISE), and optical astrometry from Gaia DR3. After applying morphological and color-based cuts to remove contaminants such as brown dwarfs and red galaxies, we performed a custom-made SED fitting using quasar and brown-dwarf templates. Statistical outputs including ̧hi^2, the Bayesian information criterion $(BIC)$, and F_ test were used to rank and select candidates. Our final catalog contains 6104 high-redshift quasar candidates within the redshift range of 4.5 < z < 7. These sources have detections in seven or more photometric bands and satisfy our SED-based statistical selection criteria (e.g., BIC > 0 and F_ test > 10). Initial spectroscopic validation using the New Technology Telescope (NTT) with the ESO Faint Object Spectrograph and Camera v.2 (EFOSC2) and the Palomar Observatory Hale Telescope with the Next Generation Palomar Spectrograph (NGPS) confirmed three high-redshift quasars at z > 5 out of six observed candidates.