Ne utron-capture Elements in M15

1. Neutron-capture Elements in M15 Kaori Otsuki (U Chicago), S. Honda, W. Aoki, T. Kajino (NAOJ) J. W. Truran, V. Dwarkadas, A. Medina (U Chicago) G. J. Mathews (UND) JINA Frontiers 2005 (8/22/2005)

2. Universal abundance pattern for Z>56 same event primary process r-process elements in field stars(1)Universal abundance pattern (Sneden et al.2000)

3. r-process elements in field stars(2)[Ba/Fe] scatter Chemical inhomogeneity of early galaxy Two events: Forms Ba & Fe Forms Fe without Ba Honda et al. 2004 Ba & Fe are formed in SNe II not all SNe II generate r-process elements ex. All SNe eject Fe but only particular progenitor mass SNe eject r-process elements (e.g., Ishimaru & Wanajo 1999, Tsujimoto et al. 1999) Today Past

4. r-process elements in field stars(3)[Sr/Ba] scatter Honda et al. 2004 There are (at least) two r-process sites: main r-process: Forms all r-process elements weak r-process: Forms Sr (Y, Zr) but not Ba Totally different events? Different progenitor mass SNe? Different phase of same event?

5. Globular cluster M15 Globular clusters • ~104-6 stars, ~106M8 • same [Fe/H] within 10% *few exceptions • not affected by explosive event after their formation Sneden et al. (1997, 2000) star-to-star variation of Ba in M15 Sneden et al. (2000) no s-process enrichment in M15 Difficult to explain with current theoretical models Constraints on GC formation models & the origin of r-process elements

6. Observations Seven red giants in M15 using Subaru/HDS • Three high Ba stars and four low Ba stars from Sneden et al.(1997) • July 25,26 2004 • 3550-5250 A, R=50,000 • One star(K479) is excluded for this discussion wide spectral lines significant contribution from other stars? (but no signature of contamination in slit viewer nor HST image.)

7. Heavy r-process elements La, Eu in M15formed only by main r-process star-to-star abundance variation in heavy neutron-capture elements Burris et al.2000 Arlandini et al.1999 No significant s-process contribution

8. Uniform weak r-process enrichment inhomogeneities of main r-process enrichment Light r-process elements Y, Zr in M15formed by main r & weak r-process Otsuki et al. (2005) main r-process at the later stage consistent with Galactic chemical evolution models Tumlinson(2005), Travaglio et al.(2001), Ishimaru et al.(2005)

9. Self-enrichment models Weak r-processes Main r-processes Pre-enrichment models Ex. clouds collisions Globular cluster 1st generation stars from metal-free PGCC 1st generation SNe induce 2nd generation star formation Main r-processes face-on collision of clouds shock induce star formation Chemically enriched cloud Globular cluster Weak r-processes Globular cluster formation Weak r-process event  complete mixing of gas  main r-process events light SNe II or massive SNe II of 2nd generation

10. ? ? Neutron-capture elements in other globular clusters Is there s-process enrichment from cluster stars? Field stars: Simmerer et al. 2004(black closed triangles), Wolf et al. 1995 (black open triangle), Honda et al. 2004(crosses) GCs: M15: Sneden et al. 2000b(circles), Our new data (squares), M68: Lee et al. 2005, M92: Our new data, M13 & M3: Sneden et al.2004 (closed circles), Cohen & Melendes 2005 (open circles), M5: Ivans et al. 2001 (closed circles), Ramirez & Cohen 2003 (open circles), M4: Ivans et al. 1999.

11. Summary • We observed seven giants in globular cluster M15 using Subaru/HDS. • There is scatter of heavy neutron-capture elements in M15. • There is no significant s-process enrichment in M15. • Light r-process elements in M15 also show abundance variations. uniform weak r-process + uneven main r-process main r-process in the later stage of globular cluster formation