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The chemistry of (not that) simple stellar populations: extragalactic globular clusters

The chemistry of (not that) simple stellar populations: extragalactic globular clusters. M.Kissler-Patig (ESO) Collaborators: T.Puzia (his PhD), D.Thomas, C.Maraston, R.Saglia, R.Bender, P.Goudfrooij, T.Richtler, M.Hempel. Extragalactic Globular Clusters.

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The chemistry of (not that) simple stellar populations: extragalactic globular clusters

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  1. The chemistry of (not that) simple stellar populations:extragalactic globular clusters M.Kissler-Patig (ESO) Collaborators: T.Puzia (his PhD), D.Thomas, C.Maraston, R.Saglia, R.Bender, P.Goudfrooij, T.Richtler, M.Hempel M.Kissler-Patig, ESO

  2. Extragalactic Globular Clusters M.Kissler-Patig, ESO

  3. Globular clusters or integrated light? Integrated light: + tracer of most mass + bright (easily observed] - studied at small radii - composite stellar pop, luminosity weighted = complicated to understand Globular clusters: + simple stellar pops (easier age determination] + studied at large radii (2-3 Reff], also traces halo pop - only 1% of total mass - link to SF less trivial M.Kissler-Patig, ESO

  4. Our project (FORS+ISAAC/VLT] SPECTRO PHOTOMERY (FORS2/ISAAC) 3500-6000A [5A] B, V, R, I, K (in seconds) NGC 1380 7h ......, 700, ......, 700, ...... NGC 2434 7h ......, 700, ......, 700, ...... NGC 3115 3h 160, 300, 160, 300, 15500 NGC 3379 4.3h ......, 300, ......, 300, ...... NGC 3585 7.5h 800, ......, ......, 800, ...... NGC 5846 9h 900, 300, 160, 300, 10000 NGC 7192 8.75h 900, 600, 900, 600, 12000 Photometry + Spectroscopy: (Puzia et al. A&A in press)

  5. Hitting globular clusters Controlling the sample: Target selection in • Color-color diagrams • Color-magnitude diagrams Hit-rates of >90% in confidence regions M.Kissler-Patig, ESO

  6. Measuring Lick indices Increasing Mgb strength M.Kissler-Patig, ESO

  7. Results: two different populations Metal-poor clusters: • homogeneous halo pop. • old ages >10 Gyr • no/little age spread (Kissler-Patig 2002, Ap&SS. 281, 487] Metal-rich clusters: • large spread in age • younger mean age • small HB effects possible • (see also Poster by Maren Hempel) SSP models from Maraston et al 2002 M.Kissler-Patig, ESO

  8. Results:  element ratios Metal-poor clusters: • large spread in /Fe, but narrow dynamic range Metal-rich clusters: • “young” clusters have close to solar /Fe • “old” clusters have high /Fe ratio, similar to the diffuse light of their hosts SSP models from Thomas et al 2002 M.Kissler-Patig, ESO

  9. Summary from spectroscopy • Metal-poor globular clusters are homogeneous in age and old -- their -elt are uncertain • Metal-rich globular clusters show a large spread in age • Old metal-rich globular clusters have high -elt abundances, similar to the integrated light of their (giant elliptical) hosts • Young metal-rich globular clusters have lower -elt abundances M.Kissler-Patig, ESO

  10. Conclusions • Globular clusters are the best tracers for star-formation epochs in early-type galaxies • Many early-type galaxies show recent star formation • Quantifying the amount of recent star formation is still uncertain (but we are working on it…) • The oldest star-formation events produced higher -elt ratio that recent ones M.Kissler-Patig, ESO

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