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Aaron Dotter (STScI) HotSci 20 July 2011

The Galactic Globular Cluster Age-Metallicity Relation and the Formation of the Galaxy. Aaron Dotter (STScI) HotSci 20 July 2011. Based on “ Globular clusters in the outer Galactic halo: new HST/ACS imaging of 6 globular clusters and the Galactic globular cluster age-metallicity relation ”

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Aaron Dotter (STScI) HotSci 20 July 2011

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  1. The Galactic Globular Cluster Age-Metallicity Relation and the Formation of the Galaxy Aaron Dotter (STScI) HotSci 20 July 2011

  2. Based on “Globular clusters in the outer Galactic halo: new HST/ACS imaging of 6 globular clusters and the Galactic globular cluster age-metallicity relation” A. Dotter, A. Sarajedini, & J. Anderson ApJ in press—arxiv:1106.4307

  3. INTRODUCTION Globular cluster ages and metallicities provide important insight into their host galaxy's chemical evolution—even if that galaxy is no more. Milky Way GCs Harris (2010) Inside/Outside Solar Circle: 2/1

  4. Omega N6397 47T ω Cen NGC 6397 47 Tuc Very Blue HB B/(B+R)=[N/A] ∆(V-I)=0.97 Blue HB B/(B+R)=0.96 ∆(V-I)=0.94 Red HB B/(B+R)=0 ∆(V-I)=0.15 Jay Anderson

  5. The 2nd Parameter & Halo Formation RGC < 5 8 < RGC < 12 Metallicity→ 5 < RGC < 8 RGC > 12 Searle & Zinn (1978) Red→ HB Morphology → Blue

  6. The HST Era HST/WFPC2 covered RGC > 50 kpc (5 GCs) HST/ACS covers > 70 GCs: RGC < 20 kpc well covered by the HST/ACS Survey of Galactic GCs RGC = 30-50 kpc and 15-20 kpc complete with Cycle 17 follow-up RGC = 20-30 kpc not done! HST/WFC3: none yet, several underway . . .

  7. Age and HB Morphology ? RGC < 5 8 < RGC < 12 Metallicity→ 5 < RGC < 8 RGC > 12 Searle & Zinn (1978) Red→ HB Morphology → Blue Age (Gyr)

  8. Age and HB Morphology Intrinsic Properties Metal-rich ⇒ Red HB Intermediate ⇒ ? Metal-poor ⇒ Blue HB ~70 GCs Δ(V-I)

  9. Age and HB Morphology Δ(V-I)

  10. Age and HB Morphology Δ(V-I)

  11. Age and HB Morphology Δ(V-I)

  12. Age and HB Morphology Δ(V-I)

  13. Age and HB Morphology Δ(V-I)

  14. Age and HB Morphology Δ(V-I)

  15. The 2nd Parameter, Explained

  16. Dwarf Galaxy Chemical Evolution M54+Sagittarius from the HST/ACS Survey of Galactic Globular Clusters (Siegel et al. 2007)

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