The High Redshift Sample in the XMM-SERVS Fields

The XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) has detected 6683 sources in W-CDF-S and ELAIS-S1, two Deep-Drilling Fields of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). Among these X-ray detected sources, over 87% have reliable multiwavelength counterparts from optical to far-infrared. We present a complete sample of 43 high-redshift (z > 3.5) X-ray-detected candidates in W-CDF-S and ELAIS-S1 using optical color selection and spectral energy distribution (SED) fitting. Compared to the X-ray source catalogs, we select all spectroscopically confirmed high-z sources, and expand by three times the sample size of the high-z candidates. Our derived space density at z > 3.5 in these two fields also agrees with previous studies. We further examine the galactic properties (stellar mass and star formation rate) of these high-z candidates derived from their SED fits, which may shed light on the evolution of active galactic nuclei (AGN) and galaxies in the early universe. Our work presents a complete sample of high-z candidates for future multiwavelength follow-up studies, such as upcoming LSST data, radio surveys, and spectroscopic observations.