On the variation of carbon abundance in galaxies and its implications
  The trends of chemical abundances and abundance ratios observed in stars of
different ages, kinematics, and metallicities bear the imprints of several
physical processes that concur to shape the host galaxy properties. By
inspecting these trends, we get precious information on stellar
nucleosynthesis, the stellar mass spectrum, the timescale of structure
formation, the efficiency of star formation, as well as any inward or outward
flows of gas. In this paper, we analyse recent determinations of carbon-to-iron
and carbon-to-oxygen abundance ratios in different environments (the Milky Way
and elliptical galaxies) using our latest chemical evolution models that
implement up-to-date stellar yields and rely on the tight constraints provided
by asteroseismic stellar ages (whenever available). A scenario where most
carbon is produced by rotating massive stars, with yields largely dependent on
the metallicity of the parent proto-star clouds, allows us to fit
simultaneously the high-quality data available for the local Galactic
components (thick and thin discs) and for microlensed dwarf stars in the
Galactic bulge, as well as the abundance ratios inferred for massive elliptical
galaxies. Yet, more efforts are needed from both observers and theoreticians in
order to base these conclusions on firmer grounds.
