Stellar populations in galaxies as traced by globular clusters
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Stellar Populations in Galaxies as traced by Globular Clusters. Markus Kissler-Patig. Stellar populations in galaxies. Star formation history of galaxies. Why use extragalactic globular clusters?. Star formation = Star cluster formation (not perfect one to one relation but almost)

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Stellar Populations in Galaxies as traced by Globular Clusters

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Stellar populations in galaxies as traced by globular clusters

Stellar Populations in Galaxies as traced by Globular Clusters

Markus Kissler-Patig


Stellar populations in galaxies as traced by globular clusters

Stellar populations in galaxies

Star formation history of galaxies


Why use extragalactic globular clusters

Why use extragalactic globular clusters?

  • Star formation = Star cluster formation(not perfect one to one relation but almost)

  • Easy detection of sub-populations

  • Easy interpretation of SSPs (as opposed to luminosity weighted properties of the diffuse light)

  • Discovery of SF events that formed more clusters than stars

  • Star clusters are proven to be among the oldest objects in the universe - study of the very first SF epochs


The key discovery from globular clusters

THE Key Discovery from Globular Clusters

  • Distinct sub-populations in early-type galaxies multiple, distinct major star formation episodes

  • To explain:

  • The presence of an old, metal-poor population in all galaxies

  • The diversity of the metal-rich population

(Puzia, Kissler-Patig, Brodie, Huchra 1999)

(Zepf & Ashman 1993Geisler et al. 1993)


Old metal poor globular clusters

Old, metal-poor globular clusters

  • They trace a stellar population not detected in the diffuse light

  • They are not predicted by SAMs (Beasley et al. 2002)

(Maraston & Thomas 2000, Lotz et al. 2000)

(Harris, Harris, Poole 1999)


Old metal poor globular clusters1

Old, metal-poor globular clusters

  • Properties: (Kissler-Patig 2002)

    • Spatial distribution: Halo (spherical, extended)

    • Abundances: metal-poor (mean metallicity correlates only weakly, if at all, with galaxy property)

    • Abundance ratio: high /Fe (short timescales)

    • Masses: universal distribution (nature or nuture?)

    • Sizes: larger than the metal-rich clusters (nature or nurture?)

    • High SN: formed with few associated stars


Old metal poor globular clusters2

Old, metal-poor globular clusters

  • Interpretation: (Burgarella, Kissler-Patig, Buat 2000, Kissler-Patig 2002)

    • Formed in small fragments (dwarf galaxy analogy)

    • Formed very early on (ages, metallicity, universal)

z=10

z=5

z=3

z=1

z=0.5

z=0

very early

10%

20%

half

3/4

today

(Courtesy Felix Stoehr)


Old metal poor globular clusters3

Old, metal-poor globular clusters

  • Direct observations of their formation?

    • Star cluster of 106 M, 20 Myr … 1-5 nJy at z=6-10Just within reach of JWST…(Burgarella & Chapelon 1998)

    • If star cluster complexes are common - easier

Cluster Complexes at low z in violent environments

(Bastian, Emsellem, Kissler-Patig, Maraston 2005)

106 M at z=5.6

(Ellis, Santos, Kneib, Kuijken 2001)


Metal rich globular clusters

Metal-rich globular clusters

  • Not one homogeneous population, but clearly mixed (old + intermediate ages, large range of metallicities)

  • Includes everything that happened since z~5(3?)

    • Formation of the bulges, spheroids

    • Minor and major dissipative mergers (SF)

    • Minor and major accretion events (dissipationless)

  • The challenge: make sense of it…


Metal rich globular clusters1

Metal-rich globular clusters

  • Caveats in the interpretation: /Fe, HB morphologies

(Thomas, Maraston, Korn 2004)

(Maraston et al. 2003)


Metal rich globular clusters2

Metal-rich globular clusters

Recent results from UV-optical-NIR imaging:

Intermediate age, metal-rich populations exist in some galaxies

(Hempel, Kissler-Patig et al. 2002, 2003, 2004)


Metal rich globular clusters3

Metal-rich globular clusters

Recent results from spectroscopy:

Intermediate age, metal-rich populations exist in some galaxies

(Puzia, Kissler-Patig, Thomas, Maraston, Saglia, Bender et al. 2004, 2005)


Conclusions

Conclusions

The galaxy formation models need to explain these stellar populations:

z=10

z=5

z=3

z=1

z=0.5

z=0

very early

10%

20%

half

3/4

today


Stellar populations in galaxies as traced by globular clusters

z=10

z=5

z=3

z=1

z=0.5

z=0

very early

10%

20%

half

3/4

today

z~0.1

z~1


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