ViT-based Local Volume Dwarf Galaxy Identification (VIDA) in the CSST survey

ABSTRACT Identifying dwarf galaxies within the Local Volume is crucial for constraining the luminosity function of satellite galaxies in the nearby universe. We report the detection capabilities of dwarf galaxies within the Local Volume using the Chinese Space Station Telescope (CSST). Based on the simulated imaging data of CSST, we present VIDA, a ViT-based dwarf galaxy identification Algorithm designed for detecting Local Volume dwarf galaxies. The simulated Local Volume dwarf galaxies can be identified using a pre-processing method for ‘extended source detection’, followed by classification with a pretrained ViT-Base model. This pipeline achieves a true positive rate exceeding 85 per cent with a false positive rate of only 0.1 per cent. We quantify the detection completeness of Local Volume dwarf galaxies across a three-dimensional parameter space defined by absolute magnitude ($M_V$), half-light radius ($R_\mathrm{ h}$), and heliocentric distance, based on simulated single-exposure CSST wide-field imaging survey data. For unresolved or semiresolved dwarf galaxies, our method achieves a significantly deeper absolute magnitude detection limit compared to catalogue-based approaches, reaching $M_V = -7$ within 10 Mpc with a surface brightness threshold $\mu \sim$ 25 mag/arcsec$^{2}$ at 2–5 Mpc and $\sim$26 mag/arcsec$^{2}$ at 5–10 Mpc. While traditional matched-filter techniques based on stellar catalogues remain more effective for detecting fully resolved, extremely low surface brightness galaxies within 5 Mpc, our approach offers complementary strengths – particularly in identifying compact or more distant systems – making it a valuable tool for expanding the census of Local Volume dwarf galaxies.