COSMOS2020: Identification of High-z Protocluster Candidates in COSMOS

We conduct a systematic search for protocluster candidates at z >= 6 in the Cosmic Evolution Survey (COSMOS) field using the recently released COSMOS2020 source catalog. We select galaxies using a number of selection criteria to obtain a sample of galaxies that have a high probability of being inside a given redshift bin. We then apply overdensity analysis to the bins using two density estimators, a Weighted Adaptive Kernel estimator and a Weighted Voronoi Tessellation estimator. We have found 15 significant (>4 sigma) candidate galaxy overdensities across the redshift range 6 <= z <= 7.7. The majority of the galaxies appear to be on the galaxy main sequence at their respective epochs. We use multiple stellar-mass-to-halo-mass conversion methods to obtain a range of dark matter halo mass estimates for the overdensities in the range of similar to 10(11)-10(13) M (circle dot), at the respective redshifts of the overdensities. The number and the masses of the halos associated with our protocluster candidates are consistent with what is expected from the area of a COSMOS-like survey in a standard ? cold dark matter cosmology. Through comparison with simulation, we expect that all of the overdensities at z similar or equal to 6 will evolve into Virgo-/Coma-like clusters at present (i.e., with masses similar to 10(14)-10(15) M (circle dot)). Compared to other overdensities identified at z >= 6 via narrowband selection techniques, the overdensities presented appear to have similar to 10x higher stellar masses and star formation rates (SFRs). We compare the evolution in the total SFR and stellar mass content of the protocluster candidates across the redshift range 6 <= z <= 7.7 and find agreement with the total average SFR from simulations.