Ne utron-capture Elements in M15
description
Transcript of Ne utron-capture Elements in M15
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)
r-process elements in field stars(1)Universal abundance pattern
• Universal abundance pattern for Z>56
same event primary process
(Sneden et al.2000)
r-process elements in field stars(2)[Ba/Fe] scatter
TodayPast
Chemical inhomogeneity of early galaxy
Ba & Fe are formed in SNe II
Two events:Forms Ba & FeForms Fe without Ba
ex. All SNe eject Fe but only particular progenitor mass SNe eject r-process elements(e.g., Ishimaru & Wanajo 1999, Tsujimoto et al. 1999)
not all SNe II generate r-process elements
Honda et al. 2004
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?
Globular cluster M15
• ~104-6 stars, ~106M
• same [Fe/H] within 10% *few exceptions
• not affected by explosive event after their formation
Globular clusters
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 modelsConstraints on GC formation models & the origin of r-process elements
ObservationsSeven 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 discussionwide spectral linessignificant contribution from other stars?(but no signature of contamination
in slit viewer nor HST image.)
Heavy r-process elements La, Eu in M15formed only by main r-process
star-to-star abundance variation in heavy neutron-capture elements
No significant s-process contribution
Burris et al.2000Arlandini et al.1999
Light r-process elements Y, Zr in M15formed by main r & weak r-process
Uniform weak r-process enrichment
inhomogeneities of main r-process enrichment
consistent with Galactic chemical evolution models Tumlinson(2005), Travaglio et al.(2001), Ishimaru et al.(2005)
Otsuki et al. (2005)
main r-process at the later stage
Globular cluster formationWeak r-process event complete mixing of gas main r-process events
Pre-enrichment modelsEx. clouds collisions
face-on collision of cloudsshock induce star formation Globular clusterChemically enriched cloud
Main r-processes
Weak r-processes
Self-enrichment models
1st generation stars from metal-free PGCC
Globular cluster1st generation SNe induce2nd generation star formation
Main r-processesWeak r-processes
light SNe II ormassive SNe II of 2nd generation
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.
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