Tracing satellite planes in the Sculptor group

Context. Although substantial progress has been made in reconciling lambda cold dark matter (ΛCDM) simulations with the observed abundance and distribution of satellite galaxies, important tensions persist. Studying satellite systems around spiral galaxies thus remains key to addressing these tensions. Aims. In this series of papers, we report the first results of an ongoing systematic survey, using Dark Energy Camera images, of faint dwarf spheroidal galaxies in the vicinity of the bright late-type spiral NGC 253 galaxy, the brightest member of the Sculptor filament located at a distance of 3.7 Mpc towards Anti-Virgo. Methods. We performed a new NGC 253 satellite search by means of visual inspection, using reprocessed co-added image cutouts from the DESI Legacy image surveys, reaching a very low surface brightness regime (28.0–29.0 mag arcsec−2). We used <ns0:sc>GALFIT</ns0:sc> software to derive the photometric and structural properties of the five dwarf galaxy candidates. Results. Five new dwarf galaxy candidates have been discovered in the vicinity of NGC 253, which we named Do V, Do VI, Do VII, Do VIII, and Do IX. Assuming that they are associated with NGC 253, their total absolute V-magnitudes fall in the −7 to −9 mag range, which is typical for dwarf satellites in the local Universe. The central surface brightness tends to be extremely low for all the discovered dwarfs and falls roughly in the range of 25–26 mag arcsec−2 in the g band. We present a new list of galaxy candidates located around the giant spiral NGC 253. Conclusions. With the inclusion of these additional satellite candidates, the overall spatial distribution of the system becomes less flattened and is now broadly consistent with the analogues drawn from the ΛCDM expectations. Interestingly, the distribution appears to be rather lopsided. However, firm conclusions about the presence or absence of a correlated satellite structure are hampered, as distance information is lacking, the census of observed dwarfs in the system remains far from complete, and spectroscopic velocities are not even available for most known satellites.