Nucleosynthesis and Chemical Evolution of Galaxies

A simple and general method for solving detailed chemical evolution with delayed production of iron and other chemical elements

“…We remark on the fact that the predicted [Fe/H]-[O/Fe] relation in the MW is fit by construction using fixed values for the key free parameters νL (or SFR0), ω and τ . It is worth noting that the values of our best parameters are in agreement with previous recent studies (see, for example, Minchev et al 2013;Nidever et al 2014;Spitoni et al 2015); in particular, a typical infall time scale τ ∼ 7 Gyr and star formation efficiency ∼ 1 Gyr −1 are necessary to reproduce also the observed age-metallicity relation and the metallicity distribution function of the G-dwarf stars in the solar neighborhood (Matteucci 2001(Matteucci , 2012Pagel 2009). …”

Varying leptonic chemical potentials and spatial variation of primordial deuterium at high z

“…It is straightforward and simple to play with the standard nucleosynthesis code [14] to study the influence of different leptonic chemical potentials on the output of light elements and in Table 1 we present a number of sample calculations from which we can draw some combinations that would give a small amount of 2 H in our neighborhood (and a larger one in deuterium-rich regions). Considerations of Galactic chemical evolution [15] permit us to infer that the abundance of primordial deuterium in nearby regions where 4 He is also measured is close to the low values determined at high red-shift; we take as the best estimates for both these not necessarily the best possible fit to the data, be the but it seems too early to look for this, bearing in mind that the observational data may change. It is worth noting that if two (or all three) ξ's are permitted to vary, the nucleosynthesis limits (for a recent reference see e.g.…”

Planetary Nebulae: Abundances and Abundance Gradients

“…A recent analysis of the halo object DDDM1 (Kwitter and Henry 1998) shows that the He, N, C, O, and Ne abundances are similar to those of type IV PN in Table 1. These abundances suggest that type IV PN reflect the metal poor conditions in the halo at the time of the formation of their progenitor stars, displaying a halo-disk vertical gradient, as found years ago by Faúndez-Abans and Maciel (1988) and confirmed by Cuisinier (1993), in contrast with an essentially flat vertical gradient for disk PN (Faúndez-Abans and Maciel 1988, Pasquali and Perinotto 1993, Cuisinier 1993.…”

“…Maciel 1996, Henry and Worthey 1999, and it seems clear that an average gradient of −0.05 to −0.07 dex/kpc can be observed in the Galaxy for O/H, S/H, Ne/H and Ar/H. The PN derived gradient (Maciel and Quireza 1999, Maciel and Köppen 1994, Amnuel 1993, Pasquali and Perinotto 1993, Köppen et al 1991) is close to -and slightly lower than -the well known gradient observed from HII regions in the Galaxy (Shaver et al 1983, Afflerbach et al 1997) and in other spiral galaxies (Kennicutt andGarnett 1996, Ferguson et al 1998). Recent work on open cluster stars confirms these results (Friel 1999, Phelps, this conference), and also data on B stars, as recently discussed by Smartt and Rolleston (1997), Gummersbach et al (1998), and Smartt (this conference), in contradiction with earlier work on these objects, which reported essentially flat gradients.…”

“…Chemical evolution models for the Galaxy can be included in one of four main classes: (i) analytical models, (ii) classical models, (iii) multiphase models and (iv) chemodynamical models (see for example Pagel 1997, Matteucci 1996. These models share a common characteristic, that is, they have to satisfy a series of observational constraints, most of which are related to the determination of chemical abundances.…”