Single-age,
single-metallicity stellar populations
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SSPs parameter coverage: |
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IMF |
Metallicity |
Age (Gyr) |
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Line-strengths, colours,
mass-to-light ratios, surface brightness fluctuations (SBFs)
Photometric predictions
The
following predictions are provided for SSPs covering
a large range of ages, metallicities and IMF types
and slopes:
·
Colours
·
Magnitudes
·
Mass-to-light ratios
·
Surface Brightness Fluctuations (SBFs)
and their corresponding colour fluctuations
The
following filter systems are used for the photometric predictions described
above:
·
U,B,V,J,H,K (Johnson)
·
R,I (Cousin)
·
F439W,F555W,F675W,F814W (WFPC2-HST).
The appropriate references for these predictions are Vazdekis et al. 1996 and Blakeslee, Vazdekis
& Ajhar (2001) (for the SBF and WFPC2 HST
filter system predictions).
Absorption
line-strengths
A number of absorption line-strengths are predicted on
the basis of the, so-called, empirical fitting functions:
·
The 21 line-strengths of the Lick/IDS system computed
on the basis of the Worthey et al. 1994 (ApJS,94,687) fitting funct. The lines
strengths are given on the Lick/IDS instrumental response. The spectral resolution depend on the wavelength range. A detailed
description of this system is given in Worthey & Ottaviani
1997 (ApJS,111,377).
Warning: to compare these line-strengths with those measured on galaxy
spectra, the data should be transformed to the characteristic
wavelength-dependent resolution and instrumental response curve of the LICK/IDS
system (see Worthey & Ottaviani
1997 (ApJS,111,377)). See Vazdekis 1999 for a discussion
on the limitations of this method and for an alternative approach.
·
The 4 higher order Balmer
lines of Worthey & Ottaviani
1997 (ApJS,111,377), also on the Lick/IDS instrumental
system.
· The 4000Å break on the basis of the fitting functions of Gorgas et al 1999 (A & AS,139,29).The system is under flux-calibration response curve. The resolution is irrelevant.
·
The near-IR CaII triplet (CaT*) and Paschen (PaT) indices of Cenarro et al. (2001) computed on the
basis of fitting functions of Cenarro et al. (2003). The system is
under flux-calibration response curve and the resolution is 1.5Å (FWHM).
Spectral energy distributions (SEDs) at
moderately high resolution
SEDs at moderately high resolution are provided for the following spectral
ranges:
·
SEDs at 1.8Å (FWHM) in
the spectral range 3855-4476Å. The model employs the extensive flux-calibrated
empirical stellar library of Jones 1999 (Ph.D. thesis, Univ. North
·
SEDs at 1.8Å (FWHM) in
the spectral range 4795-5465Å. The stellar library of Jones 1999 (Ph.D. thesis,
Univ. North
·
SEDs at 1.5Å (FWHM) in the spectral range
8349-8952Å. The
model employs the extensive flux-calibrated empirical stellar library of Cenarro et al. 2001, and the reference for the models
is Vazdekis et al. (2003). A full description of this stellar
spectral library can be found here.
·
SEDs at 2.3Å (FWHM) in
the spectral range 3540-7410Å. These model SEDs are based
on a new empirical stellar spectral library called MILES Sánchez-Blázquez et al. (2006). Until the paper that presents
these models gets published, an example for referencing these predictions would
be: … an
updated version of Vazdekis (1999) models on the
basis of MILES stellar library (Sánchez-Blázquez et
al. 2006; Cenarro et al. 2007).
These SEDs can be used to
analyze galaxy spectra in a very easy and flexible way, allowing us to adapt
these models to the characteristics of the data instead of proceeding in the
opposite direction as, for example, we must do when working on the Lick/IDS
instrumental dependent system. The SSP spectra, with flux-calibrated response,
can be smoothed to match the resolution of the data and galaxy internal
velocity dispersion, allowing us to analyze the observed spectrum in its own
system. Therefore the entire observational spectrum can be compared at one
time, or the analysis can be done by means of a particular set of features,
which should be measured on both, the galaxy spectrum and the SSP SEDs. These SEDs have been used
for studying, for example, the most relevant stellar population parameters such
as ages, metallicities, abundance ratios, IMF (e.g. Vazdekis
1999, Vazdekis et al. 2001a, Kunstchner et al. 2002, Cenarro et al. 2003, Falcón-Barroso
et al. 2003a), definition of
new age indicators
( Vazdekis & Arimoto 1999, Vazdekis
et al. 2001b), nebular emission correction (e.g. Kunstchner et al. 2002), kinematic
parameters determination (e.g. Vazdekis & Arimoto
1999, Falcón-Barroso et al.
2003b) among many other applications.
Appropriate SOFTWARE
FOR MEASURING LINE-STRENGTHS on synthetic and observational
spectra can be found here.