PÉGASE-HR (
Le
Borgne et al. 2004) is a code aimed at computing synthetic evolutive
optical spectra of galaxies with a very high resolution (R=10 000, or
dlambda=0.55) in the range Lambda=[4000, 6800] Angstroms.
PÉGASE-HR is the result of
combining the code
PÉGASE.2
with the high-resolution stellar library
ÉLODIE. This code can also be used at
low resolution (R=200) over the range covered by the BaSeL library (from
far UV to the near IR), and then produces the same results as
PÉGASE.2.
- PÉGASE.2 :
The PÉGASE.2 code (Version 2 of PÉGASE, Projet d'Etude des
GAlaxies par Synthese Evolutive in French) is aimed at modeling the
spectral evolution of galaxies. It is based on stellar
evolutionary tracks from the "Padova" group, extended to the thermally
pulsating asymptotic giant branch (AGB) and post-AGB phases; these
tracks cover all the masses, metallicities and phases of interest for
galaxy spectral synthesis. For a given evolutionary scenario
(typically characterized by a star formation law, an initial mass
function and, possibly, infall or galactic winds), the code consistently
computes the star formation rate and the metallicity of gas and stars at
any time. The nebular component (continuum and lines) due to HII
regions is roughly calculated and added to the stellar component.
Depending on the type of galaxy (disk or spheroidal), the attenuation of
the spectrum by dust is then computed using the outputs of a radiative
transfer code; this code takes into account scattering.
PÉGASE.2 uses the BaSeL (Lejeune et al. 1997,1998) library of
stellar spectra and can therefore synthesize low-resolution (R~200)
ultraviolet to near-infrared spectra of Hubble sequence galaxies as well
as of starbursts.
In PEGASE-HR, the BaSeL library is
replaced by a grid of spectra interpolated from the high-resolution ÉLODIE library of stellar spectra.
- ÉLODIE
: The ÉLODIE
library is a stellar database of 1959
spectra for 1503 stars, observed with the echelle spectrograph
ÉLODIE on the 193 cm telescope at the Observatoire de Haute
Provence. Previous versions of the library are presented in Prugniel
& Soubiran (2001) and Soubiran
et al. (1998); Katz
et al. (1998). It has been updated for the present work by
doubling the number of spectra, which greatly improved the coverage of
the parameter space (in effective temperature, surface gravity, and
metallicity).
The data reduction has also been improved, in particular the flux
calibration, and the wavelength range has been extended to 400-680
nm. For the purpose of population synthesis, the original
resolution R=42 000 has been reduced to R=10 000 at lambda=550 nm, or
more precisely to a gaussian instrumental profile of FWHM~0.55 A over
the whole range of wavelengths. The typical signal-to-noise (S/N)
ratio of the spectra is 500/A.
The HR diagram coverage with the estimated stellar parameters is
extensive (see also a detailed description in the paper or here)
- 0.27<log g ([cm/s2])<4.97
- 3185 K < Teff < 55200 K
- -3.21 < [Fe/H] <1.62.
The up-to-date version of the library of stellar spectra is available
at http://www.obs.u-bordeaux1.fr/m2a/soubiran/elodie_library.html
where fully reduced spectra, as well as the estimated stellar
parameters, are provided.
2. Collaborators
The PÉGASE-HR
Team gathers the following people in France:
Simple Stellar Populations (SSPs)
We provide here some some evolutive spectra of SSPs computed with
PÉGASE-HR, for two IMFs (Salpeter (1995) and Rana &
Basu (1992), both with Minf=0.09 Msun, Msup=120 Msun), and for a wide
range of ages (from 10^7 to 2x10^9 yr) and metallicities.
The outputs of PÉGASE-HR are primarily provided as binary FITS
files because of the large amount of information they contain. A tool
available below enables an easy convertion of these FITS files to the
old PEGASE.2 ascii format. We provide here both formats for SSPs.
These files contain all the information contained in the outputs of
PÉGASE.2 's code "spectra.f".
They also include some measurements of Lick indices on the stellar
continuum.
HR results version 3.0 correspond to the Le Borgne et al. (2004) paper.
HR results version 3.1 correspond to a newer ELODIE library (Prugniel et al 2007, astro-ph/703658).
We also provide the corresponding PÉGASE.2 spectra because they
contain precious information (colors).
The format of the FITS files is the following :
Header of HDU 0 : description of the scenario and of
the caracteristics of the FITS file (ntimes, nlambda, lambda_ref,
delta_lambda, etc.)
HDU 0 : Binary image of the evolutive spectra
(size : nlambda x ntimes)
HDU 1 : Evolution of the nebular lines. (Same
model of HII regions as in PÉGASE.2.)
HDU 2 : Some Lick indices measured on the
spectra.
HDU 3 : Evolutive physical parameters (time,
masses, SFR, Lbol, etc.).
4. Codes
- The PÉGASE-HR package
is available for download in two parts:
- The full package (v1.3) which contains the source code, the low resolution "BASEL" library, and two versions of the ELODIE libraries v3.0 and v3.1, is here (older v1.1 version is also available here). You can view the history of the versions here.
- The ELODIE grid, necessary to compute high resolution synthetic
spectra, is also available in its 3.0 version (corresponding to the Le Borgne et al. 2004 paper) here (150 Mo).
- A new version of the ELODIE grid (v3.1, see Prugniel et al 2007, astro-ph/703658) extended down to 3900 Angstroms is also available for download here.
The package comes along with a README
file which sometimes refers to PÉGASE.2's readme itself.
Its compilation is explained in the INSTALL file (it consists in the
standard ".configure" and "make" commands) or in the README file.
It is then possible to compute any synthetic evolutive spectrum with
scenarios defined with the same parameters as in PÉGASE.2.
- Conversion from FITS to ascii
format : the code fitstodat.f included in the package converts a
PÉGASE-HR's ".fits" file to a ".dat" ascii file, in the same
format as used in PEGASE.2. The information on the Lick indices is lost
in the translation.
Last modification : 27 August
2010
leborgne@iap.fr