Stellar population properties of bulges
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Stellar population properties of bulges
Daniel ThomasMax-Planck-Institut für extraterrestrische Physik, Garching
Stellar population properties star formation episodes Current status in the literature
Imaging, structural parameters, Fundamental Plane Absorption line index diagnostics
Ages and element ratios along the Hubble sequence Continuity from elliptical galaxies to bulges? Fingerprints of secular evolution?
Conclusions
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Stellar population properties of bulges
Daniel ThomasMax-Planck-Institut für extraterrestrische Physik, Garching
Stellar population properties star formation episodes Current status in the literature
Imaging, structural parameters, Fundamental Plane Absorption line index diagnostics
Ages and element ratios along the Hubble sequence Continuity from elliptical galaxies to bulges? Fingerprints of secular evolution?
Conclusions
Reviewof
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Chemical enrichment
SNII Mg, FeSNIa Fe
Enrichment ofIron is delayed
Supernova Ia
Elliptical galaxies
Thomas, Maraston, Bender 2002Trager et al. 2000
Thomas, Greggio, Bender 1998Greggio & Renzini 1983
Solar neighbourhood
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Calibration: Maraston, Greggio, Renzini et al. 2003, A&A
Thomas, Maraston, Bender, 2003a, MNRAS, 339, 897
Based on Maraston (1998) Fuel consumption theorem (Renzini & Buzzoni 1986) Stellar atmosphere calculations (Tripicco & Bell 1995; Korn, Maraston, Thomas in prep.) Extension of method introduced by Trager et al. (2000) Abundance ratio effect “semi-theoretically” included www.mpe.mpg.de/~dthomas
New stellar population model
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Stellar model atmosphere calculations
Cou
rtesy
: A
. K
orn
Tripicco & Bell 1995; Korn, Maraston, Thomas, in preparation
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Calibration
Horizontal branchMorphology
(Maraston & Thomas 2000)
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Stellar populations of bulges and disks
α/Fe and age as tracer of star formation secular evolution as star formation
Bulge properties as function of spiral type bulge versus disk
role of secular evolution
Bulges versus elliptical galaxies are bulges small ellipticals?
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Previous work (Imaging)
Fainter bulges in later spirals have
exponential profiles (WFPC2 F606W; Carollo et al. 1998)
Bulges of in later spirals more elongated (NICMOS H-band images; Fathi & Peletier
2003)
Recent star formation in later-type bulges?Fingerprints of secular evolution?
Bulges in later type spirals have steeper color gradients and are younger (optical/NIR color maps; Balcells & Peletier 1994; Peletier et al. 1999)
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Previous work (FP)
Major sequence defined by ellipticals and bulges in κ-space, bulges below the FP (Bender et al. 1992)
Offset to FP more pronounced in bulges of late-type spirals (Falcón-Barroso et al. 2002)
Flattened bulges in later-type spirals have shallower σ-profiles (Falcón-Barroso et al. 2003b)
Bulges in earlier type spirals old like ellipticals.Bulges in later type spirals younger secular evolution?
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Previous work (absorption line indices)
Bulges are Mg/Fe-enhancedlike elliptical galaxies
(Fisher et al. 1995; Idiart et al. 1996; Jablonka et al. 1996; Casuso et al. 1996)
CaT-σ like ellipticals (Saglia et al. 2002; Falcón-Barroso et al. 2003)
“Negligible influence of disk material”
Jablo
nka
et a
l. 1996
Cases of low Mg/Fe + younger age (Bender & Paquet 1995; 1999) Secular evolution in S0s?
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Current work (absorption line indices)
Trager & Dalcanton (2001, AAS)
“Determine metallicity and age in order to follow the hypothesis
that late-type bulges form from disk instabilities.”
Sauron collaboration + M. Carollo
Analysis and data unpublished
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Current work (absorption line indices)
Gorgas, Jablonka, Goudfrooij (1999, 2002) 28 edge-on spirals, 4h per object on 4m
4” off from center avoiding dust lanes, gradients up to > 1 Re Galaxy type from S0 – Sc, wavelength range 3900 ≤ λ ≤ 5500 Å
Ages and Mg/Fe ratios similar toellipticals
Index gradients independent of Hubble type
“Less compatible with secularevolution model”
Preliminary, qualitative data analysisData unpublished
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Current work (absorption line indices)
Proctor & Sansom (2002, MNRAS) 32 objects (11 Es, 6 S0s, 16 bulges) Exposure ≤ 1h per object on 4m Edge-on, minor axis, avoiding dust lanes Galaxy type from S0 – Sbc Wavelength range 4000 ≤ λ ≤ 5500 Å Balmer indices corrected for emission
Ages and Mg/Fe ratios of bulgeslower than ellipticals
“Sharp differences between early andlate types”
Mass-metallicity relation only for bulges
Disk contamination unclear, no gradientsSecular evolution not discussed
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Data: Proctor & Sansom 2002Index-index diagramsE
S0S0aSaSabSbSbc
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Contamination of line indices
Puzia, Kissler-Patig, Thomas, et al. 2003
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Calibration with globular clusters
Thomas, Maraston, Korn 2004, MNRAS Letters, in press
Data
: Mara
ston
et a
l. 20
03
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Data: Proctor & Sansom 2002
ES0S0aSaSabSbSbc
[α/Fe]
0.00.3
MWBulge
Index-index diagrams
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Hß, Mgb, Fe5270, Fe5335HδA, Mgb, Fe5270, Fe5335Proctor & Sansom 2002
Data: Proctor & Sansom 2002Correlations with σE
S0S0aSaSabSbSbc
HδA, Mgb, Fe5270, Fe5335
MW Bulge
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Blue bulges at high-z
Ellis, Abraham, Dickinson 2001
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Secular evolution Disk contamination
Without Disk Disk material
Central valuesand gradients like ellipticals
Young centers,positive gradients unlike ellipticals
+ Central values edge-on- MW bulge fits in- No correlation with Hubble type- < 10 % effect
+ Bureau’s talk- No correlation with Hubble type
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Hß, Mgb, Fe5270, Fe5335HδA, Mgb, Fe5270, Fe5335Proctor & Sansom 2002
Comparison with EsE
S0S0aSaSabSbSbc
HδA, Mgb, Fe5270, Fe5335
MW Bulge
Ellipticals
Data
: Gon
zále
z 1993;
Beuin
g e
t al. 2
00
2;
Mehle
rt et a
l. 2003
Thomas, Maraston, Bender 2002
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Conclusions Stellar population models taking element abundance ratios into account
α/Fe ratios, ages from Hγ, Hδ
Emission contamination important issue use higher-order Balmer lines + TMB models
Bulges have younger ages and lower α/Fe than ellipticals well-defined relations with velocity dispersion
continue relationship of elliptical galaxies no trend with Hubble type
Gradients key to understand the role of the disk
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Proctor, Sansom, Reid, 2000
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Stellar Population Gradients
Mehlert, Thomas et al. 2003Saglia, Maraston et al. 2000
No age gradient in ellipticals