Abstract
We present chemical evolution models for the Galactic disk. We also present a new determination of X, Y, and Z for M17 a Galactic metal-rich HII region. We compare our models for the Galactic disk with the Galactic HII regions abundances. The Δ Y/Δ O ratio predicted from the Galactic chemical evolution model is in very good agreement with the Δ Y/Δ O value derived from M17 and the primordial helium abundance, Yp, taking into account the presence of temperature variations in this HII region. From the M17 observations we obtain that Δ Y/Δ Z = 1.97+/-0.41, in excellent agreement with two Δ Y/Δ Z determinations derived from K dwarf stars of the solar vicinity that amount to 2.1+/-0.4 and 2.1+/-0.9 respectively. We also compare our models with the solar abundances. The solar and Orion nebula O/H values are in good agreement with our chemical evolution model.
