Narrow band Indices

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Narrow band Indices
Worthey et al 94
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Worthey et al 94
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Worthey et al 94
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Definition
magnitude
Equivalent Width
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The Lick System
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Also indices at higher resolution (e.g. ewith
MILES, Vazdekis et al.2000-06)
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(No Transcript)
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Age Metallicity sensitivity (e.g. Worthey 1994)
S(Hb) 0.5 S(Fe5335) 2.6
Bressan et al 96
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a/Fe enhancement
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a-enhancement
O/FeLog(NO/NFe) - Log(NO/NFe)
Annibali et al 06
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The enhanced mixture
If base model corresponds to solar mixture then
Annibali et al 06
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Accounting for a-enhancement
Effects of a-enhancement are computed by means
of response functions
R functions for different Lick indices have been
computed by Tripicco Bell (95) and Korn et al.
(05) for different values of Teff and gravity
along Isochrones (with atmosphere models ).

• Method
• the non enhanced index is computed with FF along
  the isochrone
• The correction provided by R (as a function of
  Teff g) is then applied

e.g. Tantalo, Bressan Chiosi 98 Thomas,
Maraston Bender 04 Annibali et al. 06
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enhancement
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enhancement
DDwarf TTurn Off GGiant
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Models (Korn et al 05) vs FF
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Index dependence on element is logarithmic
Annibali et al 06
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a enhancement
Annibali et al 06
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a enhancement
Annibali et al 06
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SSP vs GCs and Galaxies
Annibali et al 06
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SSP vs GCs and Galaxies
Annibali et al 06
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a/Fe- independent index
Annibali et al 06
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A Sample of 70 Early Type Galaxies(Rampazzo et
al 05, Annibali et al 06)
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Index vsVelocity Dispersion
Annibali et al 06
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Solution
x0, y0, z0 observed values (with errors
sx,y,z) (e.g. Hb, Mgb, ltFegt)
t, Z, a age, metallicity enhancement of
the model
x, y, z predicted index values
Annibali et al 06
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Age-Z degeneracy
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AGE, Z, a/Fe
Central Values
Annibali et al 06
Gradients within galaxies
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Different data models
Different Models
Annibali et al 06
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The star formation history of early-type
galaxies as a function of mass and environment
Clemens, Bressan, Nikolic, Alexander, Annibali,
Rampazzo, 06
Analysis of SDSS E-type galaxies See
also Gallazzi, Charlot, Brinchmann White,
05 Bernardi at al, 05 06 Nelan et al. (not SDSS)
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Purpose

• The SDSS (Sloan Digital Sky Survey) early type
  galaxies observed spectroscopically
• constitute a statistically very significant sample

Main advantage of this sample is errors on
individual objects may be large but error on the
mean is small
Use this sample to derive age, metallicity,
enhancement as a function of the environment
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The Sample
All objects of DR3, observed spectroscopically
by the SDSS and classified as galaxies

• spurious entries were identified and removed
• galaxies within 5 arc seconds of other galaxies
• (most likely de-blending errors),
• galaxies with redshift condence of less than 0.7
• (they cannot be reliably placed in the volume
  limited sample)
• galaxies not reliably detected in the z-band

• volume limited sample redshift range 0.005 lt z lt
  0.1

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Early-type galaxies
1) The compactness ratio (C) as defined in the
SDSS was constrained to be less than 0.33 (see
Shimasaku et al. 2001). 2) Any object with
detected emission in the Ha line was excluded in
order to minimise the effects of Balmer emission
line infilling. 3) Well measured velocity
dispersion4) Those objects where the density of
the environment could be well determined,independe
ntly of survey boundaries
4000 galaxies 0.005 lt z lt 0.1
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Method
Adopt Lick Indices system resolution
Aperture corrections from Rampazzo et al 2005
Annibali et al 2005
Velcity dispersion corrections from SDSS Stars
Montecarlo error estimation
No Hb in-filling emission correction !
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Aperture corrections
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Velocity dispersion corrections
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Method analysis of variations !
Selected indices
Hb, Hdf, Mg1, Mg2, Mgb, Fe4383 Fe4531,
Fe5270, Fe5335, G4300, C4668
Express the observed index variation ( dI ) as a
linear combination of age (t) , metallicity (Z),
a-enhancement (a/Fe) and carbon (C/H)
variation.
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Linearityof Models
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Global Fit
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Results