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Presupernova evolution and explosive nucleosynthesis in massive stars for main-sequence masses from 13 M ⊙ to 70 M ⊙ are calculated. We examine the dependence of the supernova yields on the stellar mass, 12 C(α, γ) 16 O rate, and explosion energy. The supernova yields integrated over the initial mass function are compared with the solar abundances.1. Stellar Nucleosynthesis and the 12 C(α, γ) 16 O Rate Nucleosynthesis in massive stars is one of the major sources of nuclei in the cosmos. We present presupernova models for helium stars with masses of M α = 3.3, 4, 5, 6, 8, 16, and 32 M ⊙ as an extension of the studies by Nomoto & Hashimoto (1988). These helium star masses correspond approximately to main-sequence masses of M ms = 13, 15, 18, 20, 25, 40, and 70 M ⊙ , respectively (Sugimoto & Nomoto 1980). The systematic study for such a dense grid of stellar masses enables us to understand how explosive nucleosynthesis depends on the presupernova stellar structure and to apply the results to the chemical evolution of galaxies. We use the Schwarzschild criterion for convection and neglect overshooting. The initial compositions are: X( 4 He) = 0.9879 and X( 14 N) = 0.0121, where all the original CNO elements are assumed to be converted into 14 N during core hydrogen burning. These helium stars are evolved from helium burning through the onset of the Fe core collapse.Nuclear reaction rates are mostly taken from Caughlan & Fowler (1988). For the uncertain rate of 12 C(α, γ) 16 O, we use the rate by Caughlan et al. (1985; CFHZ85), which is larger than the rate by Caughlan & Fowler (1988; CF88) by a factor of ∼ 2.3. To examine the influence of this difference, we evolve the M α = 8 M ⊙ helium star, using the 12 C(α, γ) 16 O rate by CF88 (case 25B). [The 25 M ⊙ star model with the 12 C(α, γ) 16 O rate by CFHZ85 is denoted as case 25A.] At the end of core helium burning, the formation of the carbon-oxygen core and its composition are influenced largely by the 12 C(α, γ) 16 O rate. The larger rate results in a smaller C/O ratio, which affects the abundances of Ne, Mg, Al relative to O in the more evolved cores.Comparison of the presupernova density structures for the two cases 25A and 25B shows

We present chemodynamical simulations of a Milky-Way-type galaxy using a self-consistent hydrodynamical code that includes supernova feedback and chemical enrichment, and predict the spatial distribution of elements from oxygen to zinc. In the simulated galaxy, the kinematical and chemical properties of the bulge, disk, and halo are consistent with the observations. The bulge formed from the assembly of subgalaxies at z 3, and has higher [α/Fe] ratios because of the small contribution from Type Ia supernovae. The disk formed with a constant star formation over 13 Gyr, and shows a decreasing trend of [α/Fe] and increasing trends of [(Na,Al,Cu,Mn)/Fe] against [Fe/H]. However, the thick disk stars tend to have higher [α/Fe] and lower [Mn/Fe] than thin disk stars. We also predict the frequency distribution of elemental abundance ratios as functions of time and location, which can be directly compared with galactic archeology projects such as HERMES.