Local Group dwarf galaxy detection limit in the CSST survey

ABSTRACT We predict the dwarf galaxy detection limits for the upcoming Chinese Space Station Telescope (CSST) survey that will cover 17 500 \, deg^2 of the sky with a wide field of view of 1. 1 deg2. The point-source depth reaches 26. 3 mag in the g band and 25. 9 mag in the i band. Constructing mock survey data based on the designed photometric bands, we estimate the recovery rate of artificial dwarf galaxies from mock point-source photometric catalogues. The detection of these artificial dwarf galaxies is strongly dependent on their distance, magnitude, and size, in agreement with searches in current surveys. We expect CSST to enable the detection of dwarf galaxies with MV = −3. 0 and μ250 = 32. 0 mag arcsec−2 (surface brightness limit for a system of half-light radius rh = 250 \, pc) at 400 \, kpc, and MV = −4. 9 and μ250 = 30. 5 mag arcsec−2 around the Andromeda galaxy. Beyond the Local Group, the CSST survey will achieve MV = −5. 8, and μ250 = 29. 7 mag arcsec−2 in the distance range of 1–2 Mpc, opening up an exciting discovery space for faint field dwarf galaxies. With its optical bands, wide survey footprint, and space resolution, CSST will undoubtedly expand our knowledge of low-mass dwarf galaxies to an unprecedented volume.