OBSERVATIONS and CHEMICAL EVOLUTION With help from L. MASHONKINA, F.MATTEUCCI , B. WEHMEYER, J. COWAN, T. MISHENINA, M. PIGNATARI, N. PRATZOS, R. DIEHL, C. FROHLICH, A. ARCONES and F. K. THIELEMANN Brainstorming and Fun II: September 29-30, 2014 IMPORTANT POINTS: OBSERVATIONS 1. Can get observational constraints to models of heavy element production in the early Galaxy. 2. Observations of Ba/Eu vs. Eu/Fe in r-process stars seem consistent with the SS r-process value. 3. R-process models like waiting point and HEW give similar results for Ba/Eu. 4. f_odd is high in r-process enhanced stars and low in Eu-poor stars like HD 122563. 5. Can observe differences in light vs. heavy n-capture elements in very metal-poor stars: excess of s-process in some stars. 6. It is possible to reproduce the n-capture elements in both r-process rich and r-process poor stars by employing a combination of two model fits heavy (appropriate for stars such as CS 22892-052) and light (appropriate for stars such as HD 122563). 7. Iron peak elements show a rise at low metallicity along with scatter. 8. For a large number of open clusters a large scatter of Ba and Ba overabundances, compared to solar, were observed in the last ten years. At present it is matter of debate the origin of such anomalous abundances (see Mishenina et al. 2014, Jacobson & Friel 2013, Yong et al. 2012, D'Orazi et al. 2009). Observations are difficult to reconcile with the present understanding of neutron-capture nucleosynthesis and may require an additional process, i.e., the i(ntermediate)-process (‘Cowan and Rose 1977). One of the peculiar signatures of the i-process is to predict a [Ba/La] ratio much larger than the s-process or the r-process, within the observed spread of [Eu/La]. Herwig+2011, first observational evidence of the i-process. But post-AGB stars, likely not relevant from the GCE point of view. Liu+ et al. 2014, mainstream SiC with i-process signature; Jadhav+ 2013, Fujiya+2013 AB grains ~ solar like metallicity sources. Solar metallicity sources but difficult to find constraints if relevant for GCE? Part of the CEMP-rs stars are CEMP-i stars: Bertolli+ 2013, arXiv Herwig+2014, in prep.: Warning: the i-process can contribute up to Pb. MORE TO BE DONE IN OBSERVATIONS AND THEORY 1. Need more observations of light n-capture elements such as Mo, up to Ag. 2. More Ba/Eu observations in low metallicity stars. 3. More determinations of fractional isotopic abundances for Ba, Eu, and other elements where possible. 4. Determine more precisely stellar parameters (Teff, log g, etc.). 5. How to explain rising values of Fe-peak elements at low metallicity in SNe models and GCE models? 6. Uniform observations, spectra processing, stellar parameter and abundance determinations for a large sample of OCs. 7. Uniform analysis of all the available observations (OCs, presolar grains, CEMP stars) to constrain stellar simulations. 8. We need better nuclear data for the i-process. This is needed to produce robust i-process yields. 9. Multi-dimensional hydrodynamical simulations for the H ingestion in stellar He-rich material. 10. SNe models and GCE models must be able to reproduce the newly determined and more precise abundance values in metal-poor halo stars. GALACTIC CHEMICAL EVOLUTION MODELS A HOMOGENEOUS (same stellar physics - convection, nuclear rates etc) and COMPLETE (in stellar mass and metallicity) GRID OF STELLLAR YIELDS M: 1.5 2 3 5 7 10 12 15 20 25 35 50 70 100 130 Msun Z/Zsun = 0, 10-4 10-3, 10-2, 10-1, 3 10-1, 1, 2 (to cover evolution of halo, thin and thick disks and bulge) Models accounting for ALL available - and relevant - data sets for a given galactic system. Ex 1: For MW halo: NOT only X/Fe vs Fe/H but ALSO Metallicity distributions (requires OUTFLOW, and this changes timescales of met. evolution, important if interested in sources with different timescales, like NS mergers or AGBs). Ex 2: Dispersion (if real), may point to physical ingredients that should not be neglected e.g. in local age-metallicity relation, it may point to radial migration, but also the variation of abundances in ejecta sources. In Eu/Fe vs Fe/H of halo stars, it points to ??? (rare but then very efficient r-process sources, like NS-mergers or MHD jets?) IMPORTANT POINTS: MODELS - The chemical evolution of galaxies: massive stars occur in groups and co-evolve, - feedback and ejecta return into the cycle of matter, occurs in superbubbles - modeling and studying the evolution of superbubbles from creation through fragmentation/dissolution until formation of dense cores / SFR regions: This may be interesting by itself, shed light on abundance scatter expectations, and scale dependent aspects of chemical evolution at the sub-kpc scale - disk-halo connections could be important for the >10^8 year, - at lowest metallicites inhomogeneous models must be used to explain dispersion/scatter in abundance ratios, because average over IMF not fullfilled, yet - evolution of abundances, also shed light on infall and Galactic winds and the IGM, - exploiting new measurements: sub-mm molecular lines of isotopes, GAIA, 26Al gamma-rays, QSO and GRB absorption lines. IMPORTANT POINTS: MERGER MODELS An alternative situation suggests that both SNeII and NSM can produce Eu (Honda vs. Sneden?). The best model in this case assumes that in NSM M_Eu = 2 x 10-6 Msun is produced, the delay times can be various. SNe II should produce Eu in a range 20-50 Msun. It is very important to have Eu sources acting at early times to reproduce observations at low [Fe/H] (achievable by merger models or additional source needed?). Europium can be produced from NSM only if: the NS systems explode with a delay of 1 Myr and each event produces M_Eu= 3 x 10-6 Msun and all stars with progenitor masses in the range 9-50 Msun leave a NS as a remnant. Results: NSM+MRD SNe Europium originates from NSM plus magneto-rotational (MRD) SNe. The merging events have a fixed delay of 100 Myr. The MRD SNe are assumed to be 10% of the total number of SNe II but only for z < 10-3. What is needed to improve NS Merger Models In the future the model could be improved by assuming a delay time function AND understanding the ejecta composition of the SNe which produced the two progenitor neutron stars. If they produced regular Fe-ejecta, a shift in Fe/H is inevitable before mergers eject r-process. The results of Cescutti, assuming some inhomogenous mixing in the early phases of Galaxy evolution, should be utilized. A better more secure rate of merging of NS will also be required. Many uncertainities now. More Questions for Merger Models Question of black hole formation in early Galaxy - if 50 Msol stars are needed to make the r-process. Do we need both core collapse SNe and NS Mergers (and other sources?) to explain observed Eu/Fe?