The Explosive Yields Produced by the First Generation of Core Collapse Supernovae and the Chemical Composition of Extremely Metal Poor Stars

We present a detailed comparison between an extended set of elemental abundances observed in some of the most metal poor stars presently known and the ejecta produced by a generation of primordial core collapse supernovae. We used five stars which form our initial database and define a "template" ultra metal poor star which is then compared to the theoretical predictions. Our main findings are as follows: a) the fit to [Si/Mg] and [Ca/Mg] of these very metal poor stars seems to favor the presence of a rather large C abundance at the end of the central He burning; in a classical scenario in which the border of the convective core is strictly determined by the Schwarzschild criterion, such a large C abundance would imply a rather low C12(alpha,gamma)O16 reaction rate; b) a low C abundance left by the central He burning would imply a low [Al/Mg] (<-1.2 dex) independently on the initial mass of the exploding star while a rather large C abundance would produce such a low [Al/Mg] only for the most massive stellar model; c) at variance with current beliefs that it is difficult to interpret the observed overabundance of [Co/Fe], we find that a mildly large C abundance in the He exhausted core (well within the present range of uncertainty) easily and naturally allows a very good fit to [Co/Fe]; d) our yields allow a reasonable fit to 8 out of the 11 available elemental abundances; e) within the present grid of models it is not possible to find a good match of the remaining three elements, Ti, Cr and Ni (even for an arbitrary choice of the mass cut); f) the adoption of other yields available in the literature does not improve the fit; g) since no mass in our grid provides a satisfactory fit to these three elements, even an arbitrary choice of the initial mass function would not improve their fit.Comment: 30 pages, 8 figures, 8 tables. Accepted for publication on Ap

Galaxy Evolution tool: Construction and Applications

We present a dual-infall galactic chemical evolution model which uses a new set of stellar yields calculated by Limongi et al (2001) to constrain the amount of iron-peak elements ejected by massive stars. The age-metallicity relation, G-dwarf distribution and evolution of abundance ratios are predicted using Galaxy Evolution tool (GEtool), a software package currently being developed to self-consistenly model the chemical and spectral evolution of disk galaxies. A comparison with results obtained using the Woosley & Weaver (1995) core-collapse supernova models suggests that the observed behaviour of key abundance patterns cannot be reproduced if the iron yield of massive stars increases with initial mass.Comment: 2 pages, 4 figures, to appear in "The Evolution of Galaxies II: Basic Building Blocks", (2002) ed. M. Sauvage et al. (Kluwer

Explosive yields of massive stars from Z=0 to Z=Zsun

We present a new and homogeneous set of explosive yields for masses 13, 15, 20, 25, 30 and 35 Msun and metallicities Z=0, 10^{- 6}, 10^{- 4}, 10^{- 3}, 6x10^{- 3}, 2x10^{-2}. A wide network extending up to Mo has been used in all the computation. We show that at low metallicities (Z<10^{- 4}) the final yields do not depend significantly on the initial chemical composition of the models so that a scaled solar distribution may be safely assumed at all metallicities. Moreover, no elements above Zn are produced by any mass in the grid up to a metallicity ~10^{-3}. These yields are available for any choice of the mass cut upon request.Comment: Accepted for publication on The Astrophysical Journal. 41 pages, 3 figures, 1 Tabl

Presupernova evolution and explosive nucleosynthesis of rotating massive stars in the metallicity range -3 <=[Fe/H]<= 0

We present a new grid of presupernova models of massive stars extending in mass between 13 and 120 Msun, covering four metallicities (i.e. [Fe/H]=0, -1, -2 and -3) and three initial rotation velocities (i.e. 0, 150 and 300 km/s). The explosion has been simulated following three different assumptions in order to show how the yields depend on the remnant mass - initial mass relation. An extended network from H to Bi is fully coupled to the physical evolution of the models. The main results can be summarized as follows. a) At solar metallicity the maximum mass exploding as Red Super Giant (RSG) is of the order of 17 Msun in the non rotating case, all the more massive stars exploding as WR stars. All rotating models, vice versa, explode as Wolf-Rayet (WR) stars. b) The interplay between the core He burning and the H burning shell, triggered by the rotation induced instabilities, drives the synthesis of a large primary amount of all the products of the CNO, not just N14. A fraction of them enriches enormously the radiative part of the He core (and is responsible of the large production of F) and a fraction enters the convective core leading therefore to an important primary neutron flux able to synthesize heavy nuclei up to Pb. c) In our scenario, remnant masses of the order of those inferred by the first detections of the gravitational waves (GW150914, GW151226, GW170104, GW170814) are predicted at all metallicities for none or moderate initial rotation velocities.Comment: 245 pages, 31 tables, 38 figures. Submitted to ApJ