Stellar mass-loss, rotation and the chemical enrichment of early type
  galaxies
  We present a comparison between the [Ca,C,N/Fe]-mass relations observed in
local spheroids and the results of a chemical evolution model which already
successfully reproduces the [Mg/Fe]-mass and the [Fe/H]-mass relations in these
systems. We find that the [Ca/Fe]-mass relation is naturally explained by such
a model without any additional assumption. In particular, the observed
under-abundance of Ca with respect to Mg can be attributed to the different
contributions from supernovae Type Ia and supernovae Type II to the
nucleosynthesis of these two elements. For C and N, we consider new stellar
yields that take into account stellar mass loss and rotation. These yields have
been shown to successfully reproduce the C and N abundances in Milky Way
metal-poor stars. The use of these new stellar yields produces a good agreement
between the chemical evolution model predictions and the integrated stellar
population observations for C. In the case of N, the inclusion of fast rotators
and stellar mass-loss nucleosynthesis prescriptions improves our predictions
for the slope of the [N/Fe] vs. sigma relation, but a zero point discrepancy of
0.3 dex remains. This work demonstrates that current stellar yields are unable
to simultaneously reproduce the large mean stellar [<N/Fe>] ratios inferred
from integrated spectra of elliptical galaxies and the low N abundance measured
in the gas of high redshift spheroids from absorption lines. However, it seems
reasonable to suggest that there may be uncertainties in either the inferred
stellar or gas-phase N abundances at the level of 0.3 dex. (abriged)
