Spectral models of stars and stellar populations

by Paula R. T. Coelho and collaborators


At this website you can download theoretical spectra of stars and stellar populations computed for a wide range of parameters and applications. You can go directly to the listings of stellar spectra or stellar population models.

Links to the papers describing the different models are listed below, together with the corresponding links to the download section. Files containing whole libraries can be large, so if you want to download only a specific interval of parameters, go to the search & download interface.

Feel free to contact me in case of doubts.

 

Theoretical stellar spectra

Coelho (2014)
A new library of theoretical stellar spectra with scaled-solar and α-enhanced mixtures

This work presents a new theoretical library which covers 3000 <= Teff <= 25 000 K, -0.5 <= log g <= 5.5 and 12 chemical mixtures covering 0.0017 <= Z <= 0.049 at both scaled-solar and alpha-enhanced compositions. This library complements previous ones by providing: (i) homogeneous computations of opacity distribution functions, models atmospheres, statistical surface fluxes and high-resolution spectra; (ii) high-resolution spectra with continua slopes corrected by the effect of predicted lines and (iii) two families of α-enhanced mixtures for each scaled-solar iron abundance, to allow studies of the α-enhancement both at "fixed iron" and "fixed Z" cases.

The SED and HIGHRES FITS models can be downloaded from the links below. Contact me if you need the model atmospheres, the ODF files or the unbroadened spectra (computed at wavelength sampling of R = 300000).

» SED at low resolution: FITS files covering from 130 nm to 100 μm at a wavelength sampling of ∆logλ = 8×10−4
 
search | distribution | the whole library 36 MB

» HIGHRES: FITS files covering from 250 to 900nm and broadened by a gaussian line-spread function of RLSF = 20000 and resampled to a constant wavelength sampling of 0.02 Å. Contact me if you need the unbroadened spectra (computed at wavelength sampling of R = 300000).
 
search | distribution | the whole library 3.5 GB large file!


Coelho et al. (2007)
Spectral models for solar-scaled and α-enhanced stellar populations

These are the first models published in literature to allow one to explore in a consistent way the influence of changes in thealpha-element-to-iron abundance ratio on the high-resolution spectral properties of evolving stellar populations. The modelscover the wavelength range from 3000 Å to 1.34 micron at a constant resolution of full width at half-maximum (FWHM) = 1 Å and asampling of 0.2 Å, for overall metallicities in the range 0.005 <= Z <= 0.048 and for stellar population ages between 3 and 14 Gyr.

The synthetic stellar spectra used in these SSP models are based in the computation from Coelho et al. (2005). This library has been extended towardscool giants and their fluxes have been corrected for the effect of predicted lines, in order to improve the spectrophotometric predictions (see Section 3 in Coelho et al. 2007). These stellar spectracan be downloaded from the links below.For the stellar population models, see here.

» FITS files covering from 300 to 1300nm, spectral resolution ofFWHM = 1 Å and a sampling of 0.2 Å pix−1
 
 
search | distribution | the whole library 174 MB


Coelho et al. (2005)
A library of high resolution synthetic stellar spectra from 300 nm to 1.8 µm with solar and α-enhanced composition

This is a library of high resolution synthetic spectraranging from the near-ultraviolet (300 nm) to the near-infrared (1.8 micron).The library spans all the stellar types that are relevant to the integratedlight of old and intermediate-age stellar populations in the involved spectralregion (spectral types F through M and all luminosity classes). The grid wascomputed for metallicities ranging from [Fe/H] = -2.5 to +0.5, including bothsolar and α-enhanced ([alpha/Fe] = 0.4) chemical compositions. The syntheticspectra are a good match to observations of stars throughout the stellarparameter space encompassed by the library and over the whole spectral regioncovered by the computations.
» FITS files ranging from 300nm to 1.8micron, in steps of 0.02 Å.Each FITS file consists of two apertures (multispec IRAF format), where aperture number 1 is the normalized spectrum and aperture number 2 is the flux-calibrated spectrum.
 
 
search | distribution | the whole library 9.6 GB large file!

 Alternative downloads at:
 
MPA Data Archive
 
Spanish Virtual Observatory.
 

Stellar population models



Walcher et al. (2009)
Differential stellar population models: how to reliably measure [Fe/H] and [α/Fe] in galaxies

We present differential stellar population models, which allowimproved determinations of the ages, iron and α-element abundances of old stellarpopulations from spectral fitting. These new models are calibrated at solarabundances using the predictions from classical, semi-empirical stellar populationmodels. We then use the predictive power of fully synthetic models to computepredictions for different [Fe/H] and [α/Fe]. We show that these new differential models provide remarkably accurate fits to the integrated optical spectra of thebulge globular clusters NGC 6528 and 6553, and that the inferred [Fe/H] and[α/Fe] agree with values derived elsewhere from stellar photometry andspectroscopy. The analysis of a small sample of Sloan Digital Sky Surveyearly-type galaxies further confirms that our alpha-enhanced models provide abetter fit to the spectra of massive ellipticals than the solar-scaled ones.Our approach opens new opportunities for precision measurements of abundanceratios in galaxies.
In the link below you can download the favoured version of the differential models. They are based on the theoretical predictions from Coelho et al. (2007), calibrated to solar metallicity SSP models by Vazdekis et al. (2010).

 
 
Download file with SSP models


Coelho et al. (2007)
Spectral models for solar-scaled and α-enhanced stellar populations

These are the first models published in literature to allow one to explore in a consistent way the influence of changes in thealpha-element-to-iron abundance ratio on the high-resolution spectral properties of evolving stellar populations. The modelscover the wavelength range from 3000 Å to 1.34micron at a constant resolution of full width at half-maximum (FWHM) = 1 Å and asampling of 0.2 Å, for overall metallicities in the range 0.005 <= Z <= 0.048 and for stellar population ages between 3 and 14 Gyr.The library of synthetic stellar spectra and a stellar evolutionary tracks (ingredients to the SSP models) were both computed for three different iron abundances([Fe/H] = -0.5, 0.0 and 0.2) and two different alpha-element-to-iron abundance ratios ([alpha/Fe] = 0.0 and 0.4).We expect our fully synthetic models to be primarily useful for evaluating the differential effect of changes in the alpha/Feratio on spectral properties such as broad-band colours and narrow spectral features.
 
See available files here