Presentation on theme: "Why Galaxies care about Asymptotic Giant Branch stars S. Cristallo (INAF - Osservatorio Astronomico di Teramo) Collaborators: O. Straniero, R. Gallino,"— Presentation transcript:
Why Galaxies care about Asymptotic Giant Branch stars S. Cristallo (INAF - Osservatorio Astronomico di Teramo) Collaborators: O. Straniero, R. Gallino, L. Piersanti, I. Dominguez, M.T. Lederer
OUTLINE The importance of AGB stars Major improvements on the stellar code (FRANEC) AGB nucleosynthesis and evolution at different metallicities Very low metallicity AGBs : chemical features
Why AGBs are so important… Excellent tracings of halo structures; IR emission (effects on integrated colors); tracers of intermediate age populations (IZw18); distance indicators (Mira); production sites of LIGHT & HEAVY elements.
AGB structure (1) Chieffi et al. (1998) Straniero et al. (2005) Cristallo (2006), PhD Thesis(*) Cristallo et al. (2007) (*) available at http://www.oa-teramo.inaf.it/osservatorio/personale/cristallo/pag_in_eng.html Earth-Sun (~200 R SUN ) CORE MAIN REFERENCES:
AGB evolution at very low metallicities M=2M SUN Z=10 -4 M=1.5M SUN Z=5 x 10 -5 Cristallo et al. 2007 (ApJ 667, 489)
The proton ingestion mechanism Low time steps Time dependent mixing Rapid structure reaction Coupling between phisical and chemical evolution Large neutron densities (n n ~10 15 cm -3 ) 700 isotopes & 1000 reactions Hollowell et al. (1990) Iwamoto et al. (2004) Suda et al. (2004) Straniero et al. (2005) Campbell et al. (2007) Work in progress!! M= 0.85 M M= 1.0 M M= 1.5 M M= 2.0 M M= 2.5 M Z= 5.0 x 10 -5
The importance of using a FULL nuclear network FULLREDUCED
THE STATE OF THE ART First AGB models calculated with C-enhanced low temperature opacity coefficients, with the formation of a non-negligible 13 C-pocket and calculated with a complete nuclear network; AGB models at very low metallicity: an alternative scenario to the 13 C-pocket spread requested by observations?