Stellar Populations in Galaxies

as traced by Globular Clusters

Stellar Populations in Galaxies

as traced by Globular Clusters

Markus Kissler-PatigMarkus Kissler-Patig

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

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 ClustersTHE Key Discovery from Globular Clusters

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

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

(Zepf & Ashman 1993Geisler et al. 1993)

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

To explain:

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

•The diversity of the metal-rich population

Old, metal-poor globular clustersOld, 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)

They trace a stellar population not detected in the diffuse light

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

(Harris, Harris, Poole 1999)

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

Old, metal-poor globular clustersOld, 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

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 clustersOld, metal-poor globular clusters

z=0z=0.5z=1z=3z=5z=10

(Courtesy Felix Stoehr)

20%10%very early half 3/4 today

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

Formed in small fragments (dwarf galaxy analogy)

Formed very early on (ages, metallicity, universal)

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

Formed in small fragments (dwarf galaxy analogy)

Formed very early on (ages, metallicity, universal)

Old, metal-poor globular clustersOld, metal-poor globular clusters

Direct observations of their formation? Star cluster of 106 M, 20 Myr … 1-5 nJy at z=6-10

Just within reach of JWST… (Burgarella & Chapelon 1998)

If star cluster complexes are common - easier

Direct observations of their formation? Star cluster of 106 M, 20 Myr … 1-5 nJy at z=6-10

Just within reach of JWST… (Burgarella & Chapelon 1998)

If star cluster complexes are common - easier

106 M at z=5.6(Ellis, Santos, Kneib, Kuijken 2001)

Cluster Complexes at low z in violent environments(Bastian, Emsellem, Kissler-Patig, Maraston 2005)

Metal-rich globular clustersMetal-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…

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 clustersMetal-rich globular clusters

Caveats in the interpretation: /Fe, HB morphologies

Caveats in the interpretation: /Fe, HB morphologies

(Thomas, Maraston, Korn 2004)

(Maraston et al. 2003)

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Metal-rich globular clustersMetal-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 clustersMetal-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)

ConclusionsConclusions

z=0z=0.5z=1z=3z=5z=10

20%10%very early half 3/4 today

The galaxy formation models need to explain these The galaxy formation models need to explain these stellar populations:stellar populations:

z=0z=0.5z=1z=3z=5z=10

20%10%very early half 3/4 today

z~1 z~0.1