We aim to constrain the chemo-dynamical properties of the Sagittarius (Sgr) dwarf galaxy using carbon abundances. At low metallicities in particular, these properties reveal the early chemical evolution of a system, tracing the contributing supernovae (SNe) and how much of their ejecta eventually made it into the next stellar generation. Our sample from the Pristine Inner Galaxy Survey (PIGS) includes ~350 metal-poor ([Fe/H]~-2.0 (~6.8x10^-4^dex/ arcmin) suggests that SNe Ia contributed to the system at those metallicities, especially in its inner regions. There is a low frequency of carbon-enhanced metal-poor (CEMP) stars in our Sgr sample. At higher metallicities and carbon abundances (i.e. mostly CEMPs), this may be due to photometric selection effects, but those are less likely to affect non-CEMP stars. Given the lower average [C/Fe] in DGs, we propose using the same CEMP definition ([C/Fe]>+0.7) as that applied to the Galaxy at large ends up underpredicting the number of CEMP stars in DGs. Burthermore, for Sgr, a cut at [C/Fe]~+0.35 may be more appropriate, which brings the frequency of CEMP stars in agreement with that of the whole Galaxy.

Cone search capability for table J/A+A/690/A333/memb (*Sgr members using a kinematical selection based on Gaia)

Cone search capability for table J/A+A/690/A333/membpara (Sgr members from PIGS/AAT that have reliable measurements of metallicity, [C/Fe], and stellar parameters)