Lithium patterns, Globular Clusters formation and the Big Bang Lithium abundance Francesca D’Antona INAF-OAR Meeting in honour of Francesca Matteucci, Castiglione, Sept Paolo Ventura Roberta Carini INAF-OAR plus my coworkers Annibale D’Ercole INAF-OABo Enrico Vesperini Indiana State University Francesca Matteucci University of Trieste Chemical evolution in the Universe: the next 30 years and…

A short historical summary Fundamental discovery of the “Lithium plateau” by Spite & Spite (1982) at A(Li)~2.3 (mass fraction ~10 -9 ) Is this the “Big Bang” Lithium abundance, or is it the solar system value, 10 times larger? (at that time, the problem was the difference between pop. II results and the solar system value -3.3: no hint that WMAP would provide an “intermediate” Big Bang Lithium abundance) Meeting in honour of Francesca Matteucci, Castiglione, Sept

0.0 already at that time, and in following years, three possibilities were listed: 2) BB Li = solar system Li =  depletion of Li due to surface events in pop. II 1) BB Li = Spite’ Li  production of Li during galactic chem. evol. 3) intermediate BB Li  depletion of Li due to surface events in pop. II + production due to chem.ev. A short historical summary 1982: discovery of the “Lithium plateau” by Spite & Spite (1982) Meeting in honour of Francesca Matteucci, Castiglione, Sept

1990 data of Li chemical evolution Modelling chemical evolution of Li D’Antona & Matteucci 1990 our best model included novae massive AGB strong production by Hot BottomBurning Meeting in honour of Francesca Matteucci, Castiglione, Sept my best collaborator…

Modelling chemical evolution of Li … after D’Antona & Matteucci 1990… many models were published by others: all of them included “plausible” but “invented” and very large yields for the Lithium manifactured in the AGB phase Meeting in honour of Francesca Matteucci, Castiglione, Sept Romano, Matteucci, Ventura & D’Antona (2001) take into account Ventura’s new Li-yields for AGBs, and show that AGBs are poor contributors! Romano et al (2010) (unpublished) take into account Ventura’s new Li-yields including super-AGBs, and show that it might work!

The Cameron-Fowler (1971) model and HBB ◊ Li produced by the chain in a convective hot region, so that 7 Be is transported to cooler regions before it turns into Li. Convective mixing brings Li back to the hot region where it can be burned, but it temporarily survives in the envelope and in the atmosphere. Production of Li is linked to the 3 He abundance in the region (remnant of incomplete p-p chain) and lasts until there is 3 He Very luminous AGB stars ◊ Very luminous AGB stars  a hydrostatic, slow process: the bottom of the convective envelope reaches the H-shell burning region and nuclear reaction products are transported to the surface by convection Iben 1973, Sackman, Smith & Despain 1974, Scalo, Despain & Ulrich 1975  hot bottom convective envelopes  Hot Bottom Burning (HBB) T HBB >4 x 10 7 K Meeting in honour of Francesca Matteucci, Castiglione, Sept

Hot Bottom Burning : Li, C and O 3 He + 4 He -> 7 Be -> 7 Li (Cameron & Fowler 1971) T>4 x 10 7 K In these same envelopes, Carbon also burns, so that the Carbon star features disappear 12 C -> 14 N T>6.5 x 10 7 K A third possible processing occurs at even larger T: H- burning through the ON cycle (this may occur in the low metallicity massive AGBs and is possibly at the basis of the self-enrichment process in GCs): 16 O -> 14 N T>8 x 10 7 K Meeting in honour of Francesca Matteucci, Castiglione, Sept

HBB temperatures in pop. II O  N processing is at the basis of the O reduction in second generation stars in Globular Clusters! Meeting in honour of Francesca Matteucci, Castiglione, Sept

The O-Na anticorrelation in GCs Existence of “anomalous” stars well known from the ’80s Carretta et al A&A 450, 523 grand total of 1958 individual red giant stars in the 19 GCs of the project. [Na/Fe] and [O/Fe] ratios from GIRAFFE spectra are shown as open (red) circles; abundance ratios obtained from UVES spectra (Paper VIII) are superimposed as filled (blue) circles and show no offset from the GIRAFFE sample. Arrows indicate upper limits in oxygen abundances. halo field stars GC halo stars should “ never ” be second generation I P E Meeting in honour of Francesca Matteucci, Castiglione, Sept

GC formation is in two steps where is matter processed? FRMS (Decressin et al. 2007…) AGB-SuperAGB stars (Ventura et al & following) THE NEW PARADIGM OF GC FORMATION: after a first generation (FG) of stars is born, forming a globular cluster –or even something very different, like a dwarf galaxy-, a second star formation event, based (at least partly) on matter processed within FG stars (same Z!) gives origin to the chemically anomalous second generation (SG) stars. Loss of the ‘ environmental ’ dwarf galaxy, or of MOST of the FG stars from the former GC, leaves out a globular cluster as it is today Meeting in honour of Francesca Matteucci, Castiglione, Sept

this is the range of abundances in low metallicity field stars ?? anticorrelation models!! Models provide O depletion, Na production, but … Meeting in honour of Francesca Matteucci, Castiglione, Sept

Successful models: dilution a “ dilution ” model is necessary in order to obtain the observed anticorrelation AGB ejecta + pristine gas provide the mixture of composition that can explain the observations Meeting in honour of Francesca Matteucci, Castiglione, Sept

“ Strong ” and “ mild ” O-Na anticorrelations successful models should be able to reproduce different cases, as exemplified by NGC 2808 and M4 Meeting in honour of Francesca Matteucci, Castiglione, Sept

HST Treasury project GO13297 (Piotto) First data reduction of NGC2808 data

Chemical evolution models data from Carretta et al D ’ Ercole et al. 2012, yields from Ventura& D ’ Antona 2011 NGC ) a ‘ pure ejecta ’ SG from super- AGBs, high Y 2) an intermediate SG formed by ejecta of massive AGBs plus pristine matter reaccreted 0) FG in place Meeting in honour of Francesca Matteucci, Castiglione, Sept

Shortly: model for clusters with “strong” chemical anomalies 1: FG in place, standard C.C. Na-poor, O- rich 2: extreme SG first phases of cooling flow: C.C. of super- AGB ejecta: Na-rich, O-deprived 3: intermediate SG: mixture of massive AGB ejecta and pristine gas: C.C. moderately Na-rich and O-poor Meeting in honour of Francesca Matteucci, Castiglione, Sept

Strong dilution in clusters with ‘mild’ O-Na M4 data from Marino et al ) the ‘ pure ejecta ’ SG from super-AGBs, high Y, must be inhibited 2) mixing occurs with a larger % of pristine gas, SG formation provides small O-depletion and Y spread, some Na enhancement Meeting in honour of Francesca Matteucci, Castiglione, Sept

Shortly: model for clusters with “mild” chemical anomalies 1: FG in place, standard C.C. Na-poor, O- rich 2: extreme SG first phases of cooling flow: C.C. of super- AGB ejecta: Na-rich, O-deprived 2: SG is born directly from pristine gas contaminated by massive AGB – superAGB ejecta: C.C. moderately Na- rich and scarcely deprived in O Meeting in honour of Francesca Matteucci, Castiglione, Sept

Melendez & Ramirez Li plateau for -3<[Fe/H]<-1 (slope for Fe/H<-2.5 not included) BUT GC dwarfs seem to have a larger dispersion: is it due to the presence of SG stars? Lind et al Pasquini et al Bonifacio et al What we expect for Lithium? Meeting in honour of Francesca Matteucci, Castiglione, Sept

What we expect for Lithium? e higher M  larger T_bottom  stronger and faster Li production Meeting in honour of Francesca Matteucci, Castiglione, Sept

Metallicity dependence at M=6Msun higher Z  smaller T_bottom  smaller and slower Li production Meeting in honour of Francesca Matteucci, Castiglione, Sept

But production does not mean yield! two ingredients are important: how much Li is made, and how long it lasts  so that mass loss can recycle it in the i.s.m. AND mass loss is another big unknown parameter (both absolute values and dependence on the luminosity) Ventura et al A&A 339,215 Meeting in honour of Francesca Matteucci, Castiglione, Sept

the yield depends dramatically on mass loss! here we see the role of mass loss at Z=10 -3 Center: ‘ standard ’ Mdot Upper models: Mdot*2 Lower: Mdot from Vassiliadis & Wood Meeting in honour of Francesca Matteucci, Castiglione, Sept

In VD models, mass loss rate calibrated on Li in the MC O-rich luminous giants A(Li) decreases with initial mass due to the faster He3 destruction in spite of larger abundances reached in the envelope A(Li) re-increases due both to the stronger production and huge mass loss Meeting in honour of Francesca Matteucci, Castiglione, Sept

Observational results in some clusters M4 D’Orazi & Marino 2010 giants shifted Monaco et al turnoff stars Na-rich (SG) stars may have just 0.1 dex smaller Li than Na-poor (FG) stars! Similar results in other clusters: NGC 6397, e.g. Is there an influence of AGB Li production? Or not? Meeting in honour of Francesca Matteucci, Castiglione, Sept

Observational results in some clusters Use the D ’ Ercole et al chemical evolution model We have a further ambiguity: Which is the Lithium content of the diluting “pristine” matter? Is it the”observed” value A(Li)= , or we have to make the hypothesis that the true value is the Big Bang abundance, now given at A(Li)= ??? In the latter case, we have also to assume that the same amount of Li surface depletion takes place in SG stars… THIS CHOICE MAKES A DIFFERENCE IN THE MODEL RESULTS Meeting in honour of Francesca Matteucci, Castiglione, Sept

4: SG STARS: a) the Li at the surface is that resulting from the mixture above b) Li observed is that resulting from the mixture, but REDUCED by the same mechanism which brings pop.II Li from to Possibilities (schematically) 1: OBSERVED: FG stars A(Li)= : but in the gas forming the FG and diluting the SG: a) A(Li)= b) A(Li)= : SG GAS: mixture of gas having either a) or b) plus Li of relevant AGB ejecta Meeting in honour of Francesca Matteucci, Castiglione, Sept

model M4-3 A(Li)pristine=2.2A(Li) pristine=2.7 A(Li)=2. in ejecta of 7.5 and 8Msun A(Li)pristine=2.2 A(Li)pristine=2.7 result is OK also if we assume NO Li in the AGB ejecta, as done in the above figure… Modelling M4 Meeting in honour of Francesca Matteucci, Castiglione, Sept

The super-AGB yields seem to be very overestimated to be consistent with M4 data for Li If there is Li in the ejecta, or not, does not make any difference in the final result: We mainly need that the dilution of Na-rich gas with pristine gas is strong enough that the Lithium abundance is dominated by the primordial gas abundance The choice a) vs. b) for the primordial Li is not discriminating (unless we take seriously the super-AGB yields) Result to bring home, from modelling M4 Meeting in honour of Francesca Matteucci, Castiglione, Sept

The case of clusters with strong anomalies A(Li)pristine=2.3 A(Li)pristine=2.6 FG extreme SG intermediate SG IF the yields of super-AGBs by VD2011 are reliable, we should find a few very Li-rich stars (A(Li)=2.7-3) in the clusters having an extreme SG, born directly from super-AGB ejecta, e.g. in wCen, NGC 2808! (No evidence so far: these yields are too large?) Meeting in honour of Francesca Matteucci, Castiglione, Sept

Role of intermediate SG A(Li)pristine=2.3 Slope=0.37 A(Li)pristine=2.6 Slope = 0.6 FG extreme SG intermediate SG Meeting in honour of Francesca Matteucci, Castiglione, Sept

The case of NGC 6752 no extreme anomalies inthe O-Na anticorr. Y spread relatively small (from MS) Shen et al. (2010) show that Li and O are correlated, with a slope much smaller than 1 (corresponding to dilution with matter devoid of both O and Li) Meeting in honour of Francesca Matteucci, Castiglione, Sept slope 1

The case of NGC 6752 A(Li)pristine=2.6 A(Li)pristine=2.3  A(Li  O/Fe]=0.27±0.05  A(Li  O/Fe]=0.62±0.05 if we had 1) better oxygen – lithium data; 2) better confidence in the chemical evolution model  we could use the data as a TEST for Big Bang Lithium! Meeting in honour of Francesca Matteucci, Castiglione, Sept

Summary ◊ Still we are not sure about how to interpret the observed abundance of Li in pop. II stars ◊ Galactic evolution of Lithium requires massive AGB – superAGB as source of Lithium ◊ The Hot Bottom Burning producing Lithium is also the source of further nucleosynthesis in AGB – superAGB, and the most plausible source of the processed matter forming second generation stars in Globular Clusters ◊ Modelling of GC abundance patterns (e.g. O – Na) can be successfully achieved. This allows to predict Li distribution among GC stars ◊ The result of simulations depend on the Big Bang Lithium abundance assumed to be available in the matter diluting the AGb ejecta. Observations of Li in GCs may in the end constrain the Original Li. Meeting in honour of Francesca Matteucci, Castiglione, Sept

A MESSAGE FROM ITALO: Hi Francesca: what can I say? I’m proud of you! But I’m proud of me as well, for I could help in pushing ahead somebody who is BETTER, and not WORSE than I am! So: to the next 30 yr of research …(my art. 10)!

Francesca, best wishes for your life, and good work for the future 30yr (is this enough?) from myself and Italo, thank you, you know why

M4 D’Orazi & Marino 2010