the chemistry of (not that) simple stellar populations: extragalactic globular clusters
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
M.Kissler-Patig, ESOM.Kissler-Patig, ESO
The chemistry of (not that) simple stellar
populations: extragalactic globular
clustersM.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
Extragalactic Globular Clusters
M.Kissler-Patig, ESO
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 understandGlobular 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
Our project (FORS+ISAAC/VLT]
Photometry + Spectroscopy: (Puzia et al. A&A in press) 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
M.Kissler-Patig, ESO
Hitting globular clusters
Controlling the sample:Target selection in– Color-color diagrams– Color-magnitude
diagramsHit-rates of >90% in
confidence regions
M.Kissler-Patig, ESO
Measuring Lick indices
IncreasingMgb strength
M.Kissler-Patig, ESO
Results: two different populationsMetal-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
possibleSSP models from Maraston et al 2002
(see also Poster by Maren Hempel)
M.Kissler-Patig, ESO
Results: element ratiosMetal-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
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
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