Galactic Chemical Evolution


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Contact: F.X.Timmes
my one page vitae,
full vitae,
research statement, and
teaching statement.

"Zone models" of galactic chemical evolution usually assert the abundance $N$ of an isotope $i$ follows \begin{equation} \frac{dN_i}{dt} = \rm{death} \ - \ \rm {birth} \ + \ \rm {infall} \ + \ \rm {decay} \ . \label{eq1} \tag{1} \end{equation} The death term (representing supernovae, kilonovae, classical novae, etc) is a sum of retarded time birth terms (stars born yesterday die today) , giving rise to a system of integro-differential equations \begin{equation} \begin{split} \frac{dN_i}{dt} & = \int_{M_{lo}}^{M_{hi}} B(t - \tau(m)) \ \Psi(m) \ N_i (t-\tau(m)) \ dm \\ & - \ B(t) \ \frac{N_i}{N_{\rm{gas}}} + \ {\dot N}_{i,\rm{gas}} + \frac{N_i}{\tau_{1/2,i}} \qquad {\rm M}_{\odot} \ {\rm pc}^{-3} \ {\rm Gyr}^{-1} \ , \end{split} \label{eq2} \tag{2} \end{equation} where $B(t)$ is the birth rate, $\tau(m)$ is the stellar lifetime, $\Psi(m)$ is the initial mass function, $N_{\rm{gas}}$ is the total surface gas density, ${\dot N}_{i,\rm{gas}}$ is the mass accretion rate, and $\tau_{1/2,i}$ is the half-life of the isotope.

The tool chem3.tbz solves this system of integro-differentials. The tool includes a plain text nucleosynthesis data file, which one can easily modify, that contains isotopic contributions from Type II supernovae (Woosley & Weaver 1995), low mass stars (Renzini & Voli 1986), six different Type Ia supernovae models, three different classical novae models, and Big Bang nucleosynthesis.

Hydrogen Through Zinc

The chemical evolution of 76 stable isotopes, from hydrogen to zinc, is presented in this article. A grid of 60 Type II supernova models of varying mass (11 ≤ M/M ≤ 40) and metallicity (0, 10-4, 0.01, 0.1, and 1 Z), is coupled with a simple dynamical model for the Milky Way. The results are compared in detail with the inferred atmospheric abundances for stars with metallicities in the range -3.0 ≤ [Fe/H] ≤ 0.0 dex. Sampled 4.6 billion years ago at a distance of 8.5 kpc, we find a composition at the solar circle that is within a factor of two of the solar abundances:


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