Oral Abstract

Oral Contribution (O0.3) Sophie van Mierlo (Kapteyn Astronomical Institute)

Intermediate-redshift contaminants in the search for z>6 galaxies within the Euclid Deep survey

The upcoming Euclid space telescope is expected to discover thousands of z>6 galaxies in three so-called Deep Fields, which will encompass a total area of 40 deg2. Correctly identifying z>6 galaxies will be challenging, though, due to the limited number of Euclid filters and ancillary data availability. In this talk, I will present the results of our study of the degree of contamination by intermediate-redshift galaxies (z=2-5.8) that is expected in the search for z>6 galaxies. We have simulated Euclid and ancillary photometry from a large sample of real galaxies at z=2-8 in COSMOS, and derived redshifts and physical parameters for various combinations of Euclid, Rubin and Spitzer data. Based on Euclid data alone, we find that more than half of the apparent z>6 galaxies are actually intermediate-z interlopers, but the contamination is strongly reduced by including Rubin and Spitzer data. To further minimise contamination, we show how the z>6 contaminants can be separated from true z>6 galaxies using simple Euclid colour selection criteria once the photometric redshifts are known.