Can AGB winds explain multiple populations in globular clusters?

1. Multiple populations in
Globular Clusters
Vancouver, May 2019
Paolo Ventura
Observatory of Rome

2. The traditional paradigma that Globular
Clusters stars are simple stellar populations
has been challenged in the last decades,
thanks to the improvement in the
photometry and results from high-resolution
spectroscopy

3. Oxygen vs. Sodium in GC stars
(Carretta + 2006, A&A, 450, 523)
RGB stars
(many clusters)
NGC 2808
RGB stars
TO & SGB
stars (Gratton
et al. 2001)
NO extra-mixing

4. Bedin + 2000 (A&A 363, 159)
Peculiar
morphology of
the HB of some
clusters: typical
example NGC
2808, showing a
Na-O
anticorrelation
(Carretta +
2004,2005)

5. Y=0.38
Y=0.30
Y=.24
To explain the stars
distribution in the
HB, THREE different
populations required:
AND... Carretta et al. 2005
find three different classes
of objects in O-Na anticorr.
D’Antona & Caloi,
2004, ApJ, 611, 871

6. NGC 2808 photometry
(Piotto et al. 2007 ApJL 661, L53)

7. Metal poor GCs. I – NGC 2419
a) extreme chemistry (δ[Mg/Fe]~-1!)
Mucciarelli + 2012
b) He-rich (Y ~ 0.36) stars
Di Criscienzo + 2015

8. Metal poor. GCs II – NGC 7099
a) Na and Al spread b) No Mg spread!
Carretta + 2009
c) Little helium spread (Mucciarelli+2014)

9. Intermediate-Z GCs I – NGC 2808
a) He-rich (Y~0.37) stars
b) signature of p-capture nuclosynthesis (δ[Mg/Fe]~-0.5)
Carretta + 2015

10. Intermediate-Z GCs I – M3
a) Moderate p-capture nuclosynthesis (δ[Mg/Fe]~-0.15)
b) Stars slightly enriched in
helium (D’Antona & Caloi 2008)

11. Metal rich GCs – 47 Tuc
a) O-Na trend detected b) No Mg spread
Carretta + 2013

12. metallicity
dilution
heliumenrichment
Mg depletion

13. Self-enrichment of GCs:
hunting the polluters
1) Ejecta enriched in helium, with δY~0.12
(Y~0.37), independently of metallicity
2) Gas showing the signature of p-capture
nucleosynthesis (O-Na,Mg-Al-Si trends)
3) The degree of p-capture nucleosynthesis
(Mg depletion) sensitive to metallicity

14. Can AGB starsm ake it??

15. 1) Do AGB stars produce ejecta enriched in
helium, with Y~0.37, independently of
metallicity ?
SAGB

16. 2) Does the gas from AGB stars show the
signature of p-capture nucleosynthesis
(O-Na, Mg-Al-Si trends) ?

17. 1991A&A...244L..43B

18. 1981A&A....94..175R

19. Di Criscienzo + 2018, MNRAS, 479 5325
SAGB stars to study NGC 2808

20. 3) Is the degree of nucleosynthesis
of the gas ejected from AGB
stars sensitive to metallicity ?
[Fe/H]=-2
[Fe/H]=-1.3
[Fe/H]=-0.6

21. The AGB yields proved successful in reproducing the
Mg-Al and Mg-Si trends observed in metal poor
Globular Clusters (Meszaros + 2015, AJ,149, 153)
Ventura + 2016, ApJL, 831, L17

22. Intermediate metallicity Globular Clusters: the
case of M3 (Dell’Agli + 2018)

26. Thank you Harvey
On behalf of Rome…