Marco Limongi INAF - Osservatorio Astronomico di Roma, Italy (marco@mporzio.astro.it)

1. Nucleosynthesis Of Zero Metallicity Core Collapse Supernovae And The Abundance Pattern Of Extremely Metal Poor Stars Marco Limongi INAF - Osservatorio Astronomico di Roma, Italy (marco@mporzio.astro.it) CSPA, MONASH UNIVERSITY, Australia AND Alessandro Chieffi INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, Italy (achieffi@rm.iasf.cnr.it) CSPA, MONASH UNIVERSITY, Australia

2. Background: Normal EMPS High 12C(a,g)16O (CF85), Low C-central Low 12C(a,g)16O (CA88), High C-central (Chieffi & Limongi 2002, ApJ, 281,294, Data from Norris, Ryan & Beers 2001, ApJ, 561, 1034) • High C abundance (low 12C(a,g)16O rate): good fit to 8 of the 11 elements • [Sc/Fe] and [Co/Fe] drastically depended on the central C abundance left by He burning • No simultaneous fit to [Ti/Fe], [Cr/Fe] and [Ni/Fe] even for any choice of the mass cut

3. Background: HE 0107-5240 HE0107-5240 was born in a cloud polluted by the ejecta of a single “standard” supernova TWO MAJOR INCONSISTENCIES Int. Structure • The Mass Cut required to fit [Ca/Fe], [Ti/Fe] and [Ni/Fe] is much more internal than the one needed to fit [C/Fe] [X/Fe] • The observed ratios among the light elements only, [C/Mg], [N/Mg] and [Na/Mg], is incompatible with any Mass Cut internal to the CO core {X/Mg} The chemical composition of HE 0107-5240 is INCOMPATIBLE with the ejecta of a single POPIII Core Collapse Supernova

4. Background: TWO POPIII Core Collapse Supernovae Scenario Bonifacio, Limongi & Chieffi 2003 Nature 422,434 Limongi, Chieffi & Bonifacio 2003, ApJL, 594, L126 The most natural solution is to get the Iron peak nuclei from one SN and the lighter elements from another SN • The observed ratios among just the light elements [C/Mg], [N/Mg] and [Na/Mg] are perfectly fitted by a 35MO whose mass cut is located in the He convective shell at M ~10 MO {X/Mg} • The star providing the Iron peak nuclei must be less massive because: • The yields of the light elements must be negligible • It must have a quite internal mass cut Int. Structure A 15 MO is the ideal candidate!

5. 8 106 MO XFe ~ 6.7010-9 3 102 MO XC ~ 1.6510-4 HE0107-5240 TWO POPIII Core Collapse Supernovae Scenario 15 35

6. Updated Observations The lowest metallicity star known that exhibits an s-process signature has [Fe/H]=-3.1 Currently there are 12 stars known to have [Fe/H]<-3.5 • Similar abundance pattern of heavy elements • Similar pattern of Light Elements (7 of them) • Large enhancement and scatter of Light Elements (5 of them)

7. “NORMAL” EMPS C-RICH EMPS “Average” (AVG) can be defined representing the ensamble of all the stars sharing a similar pattern of all the elements 5 of the 12 are C-rich! Is this a common feature at the lowest metallicities? Large C, N and O overabundances  heavy element deficient (or Iron poor) stars rather than metal poor stars

8. New Zero Metallicity Models For Core Collapse SNe Grid of 8 stellar models: 13, 15, 20, 25, 30, 35, 50 and 80 MO Initial Big Bang Composition PreSN Evolution: FRANEC (ver.4.05.19) (Limongi & Chieffi 2003, ApJ, 592, 404) • 4 physical + N chemical equations fully coupled and solved simultaneously • Very Extended Fully Automated Nuclear Network 282 nuclear species (H to Mo) and ~ 3000 processes (Fully Automated) • Nuclear Burning Coupled to Time Dependent Convective Mixing • No Mass Loss, No Overshooting Explosion: piston of initial velocity v0, located near the edge of the iron core: • Explosion: 1D PPM Lagrangian Hydrocode (Colella & Woodward 1984) • Explosive Nucleosynthesis:same nuclear network of hydrostatic evolutions For each model, several hydro runs iterating on v0 in order to obtain a given Mini-Mrem(56Ni mass) relation. Explosion energies of the order of 1-2 1051 ergs

9. Initial Mass – Remnant Mass Relation Lack of autoconsistent models of explosions for Core Collapse Supernovae Initial Mass – Remnant Mass UNKNOWN The larger the mass  the larger the binding energy  the larger the remnant M > 25 MO black holes (heavy element synthesis negligible)

10. Ejecta of a population of PopIII Core Collapse SNe M > 25 MO black holes (heavy element synthesis negligible) C-rich EMPS Normal EMPS The chemical composition coming out from the pollution of a population of PopIII CC-SNe will depend on the combination between the distribution of the various masses and the efficiency of mixing the ejecta of each SN A different statistical distribution of massive stars and/or a different mixing efficiency could explain all the EMPS?

11. Ejecta of a population of PopIII Core Collapse SNe High Mass SNe Homogeneous Mixing Low Mass SNe In the case of a partial mixing between the ejecta of the various SNe the relative number of stars needed to produce a given chemical composition may change significantly

12. A general scenario to explain all the EMPS PRISTINE MATERIAL POP III Core Collapse Supernovae “C-rich EMPS” [Fe/H]=f(dilution) Enhancement=f(mixing) Scatter=f(exploding masses) “Normal EMPS” [Fe/H]=f(dilution) Pattern independent on the exploding mass Clouds Dominated by the ejecta of low mass SNe Clouds Dominated by the ejecta of high mass SNe

13. Fit to Normal EMPS Cayrel et al. 2004 Light and Intermediate Mass Elements: 1.Very well fitted up to Ca 2.Na overproduced by a factor of ~4. Difficult to explain [Na/Al] 3.K deficient by more than a factor of 10 (neutrino process?) Iron Peak Elements: 4.Cr and Mn OK (Their are made in the same zone). Ni OK 5.Sc, Ti, Co and Zn underestimated. Problem common to all standard models.

14. Fit to C-Rich EMPS: CS 22949-037 Cayrel et al. 2004 Light and Intermediate Mass Elements: 1.Very well fitted up to Ca 2.C overproduced, N underproduced (more refined grid of models) 3.K deficient by a factor of ~ 4 Iron Peak Elements: Same results as in the Normal EMPS

15. Fit to C-Rich EMPS: CS 29498-043 Aoki et al. 2004 Light and Intermediate Mass Elements: 1.Very well fitted up to Ca 2.Al slightly overestmated Iron Peak Elements: Same results as in the Normal EMPS

16. Fit to C-Rich EMPS: HE 0107-5240 Christlieb et al. 2004 Abundances corrected for 3D/NLTE effect kindly provided by Norbert yesterday! 1.Very good match for all the elements 2.Na underestimated (more refined grid of models?, 12C(a,g)16O cross section?)

17. Fit to C-Rich EMPS: HE 1327-2326 Frebel et al. 2005 Abundances corrected for 3D/NLTE effect kindly provided by Anna yesterday! 1.Very good match for all the elements

18. Conclusions • The element abundance pattern of both the NORMAL and the C-RICH EMPS can be explained in terms of enrichment of STANDARD POPIII CC-SNe of different mass and/or different mixing efficiency • Clouds dominated by the ejecta of low mass SNe NORMAL EMPS Low mass supernovae produce the same pattern independent on the mass Different distributions and/or mixing degree do not alter the pattern of all the elements Similar pattern of all the elements shown by all Normal EMPS • Clouds dominated by the ejecta of high mass SNe C-RICH EMPS High mass supernovae produce a different pattern of the light elements depending on the mass. Different enhancement and scatter of light elements shown by C-Rich EMPS

19. Conclusions • In general the observed abundance patterns of light elements are very well fitted by the models. • An improvement in the fit between the models and the observations should be obtained by the computation of a more refined grid of models On the contrary • The abundance pattern of ALL the iron peak elements are never reproduced by the models • Cr, Mn and Ni are always very well fitted by the models (Cr and Mn are made in the same zone by explosive incomplete Si burning) • Sc, Ti, Co and Zn are always heavily underestimated by the models. All these elements are produced by explosive complete Si burning! • An increase of the C abundance left by central He burning (lower 12C(a,g)16O cross section) would improve the fit to Sc, Co and Zn More efficient C burning shell  less compact structure  higher a rich freezout  increase of [Sc,Co,Zn/Fe]

20. Dependence of [Sc/Fe] and [Co/Fe] on the Central C Abundance An increase of the C abundance in the He exhausted core leads to: 1. A more flattened out final mass-radius relation because the contraction of the O-Ne core is partly slowed down by the presence of a very active C burning shell - a lower average density in the regions that experience complete and incomplete explosive Si burning - a higher a-rich freezout and a reduced amount of 56Ni synthesized - an increase of both [Sc/Fe] and [Co/Fe] for any choice of the mass cut location 2. An increase of Mg deeper mass cut in order to maintain the same [Mg/Fe] - an increase of both [Sc/Fe] and [Co/Fe]

21. An alternative scenario Recently Umeda & Nomoto (2005) proposed the following solution to improve the fit to the heavy elments: [Sc/Fe] - [Ti/Fe] Energetic explosions (10-20 foe) + Density of the presupernova model reduced by a factor of 3 + Mixing-Fallback [Co/Fe] Energetic explosion (10-20 foe) + Ye≥0.5 (Si-c zone) + Mixing-Fallback [Zn/Fe] Energetic explosion (10-20 foe) + Mixing-Fallback [Cr/Fe] No idea

22. Cx Sic Sii Ox Nex 3.3 1.9 5 4 2.1 Ye Mn 15 M Fe Ti Co Ti Cr V Ni Sc Sic Sii Ox Nex Cx K S Mass Fraction Ar Si Ca Cx Sic Sii Ox Nex He Cl O Mg Ne P Na Al C Interior Mass (M) Chemical Composition After The Explosion Remnant Ejecta Mass Cut

23. 1st Inconsistency Red Dots = Obtained by choosing the Mass Cut to fit [C/Fe] Blue Dots = Obtained by choosing the Mass Cut to fit [Ca/Fe]

24. 2nd Inconsistency • The observed ratios among the light elements only, [C/Mg], [N/Mg] and [Na/Mg], is incompatible with any Mass Cut internal to the CO core {X/Fe}star=Log(X/Fe)model - Log(X/Fe)star 4He {C/Mg} - {N/Mg} - {Na/Mg} - solid He – dotted C – dashed Mg