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, pcoelho at usp.br
Theoretical stellar spectra
Pacheco et al. (2021)
A Grid of Synthetic Spectra for Subdwarfs: Non-LTE Line-blanketed Atmosphere Models
In this work a new grid of NLTE atmosphere model spectra for hot and
moderately cool subdwarf stars is presented. High-resolution spectra
are calculated in the range from 100nm to 1,000nm.
Our grid covers eight temperatures within 10,000 <= Teff [K] <= 65,000, three
surface gravities in the range 4.5 <= log g [cgs] <= 6.5, two helium abundances
matching two extreme helium-rich and helium-poor scenarios, and two
limiting metallicity boundaries regarding both solar
([Fe/H] = 0) and Galactic halo ([Fe/H] = -1.5 and [alpha/Fe] = +0.4).
The models can be downloaded here. From filename: The number after t is Teff and the number after g is log g. The suffix represents the chemical abundances: sol_Hepoor ([Fe/H]=0 and He-poor); sol_Herich ([Fe/H]=0 and He-rich); lowZ_Hepoor ([Fe/H]=-1.5, [alpha/Fe]=+0.4 and He-poor); or lowZ_Herich ([Fe/H]=-1.5, [alpha/Fe]=+0.4 and He-rich). The reference for each He value (log(nHe/nH)) as a function of Teff is available at paper’s table 2. Example: t10000_g+4.5_sol_Hepoor.fit is the spectrum with 10000K, log g=+4.5, solar abundance and He-poor.
The files can also be accessed in Vizier and at the Spanish VO. In the future we plan on incorporating these models in the Search facilities.
Coelho, Bruzual & Charlot (2020)
To use or not to use synthetic stellar spectra in population synthesis models?
In this work we build a synthetic stellar library - SynCoMiL (Synthetic Counterpart to the MILES Library) - mimicking the coverage of an empirical library, and Stellar Population Synthesis (SPS) models with different choices of stellar library, tailored to investigate the impact of an empirical vs. a theoretical library in simple stellar population predictions.
The models can be downloaded here. SynCoMiL is given in two files: syncomil_parameters_20191027.fits lists the atmospheric parameters used as input in the calculations, syncomil_fluxes_20191027.fits gives the fluxes, one star per column (1st column gives the wavelength). SPS models are available in the subdirectories, according to the labels adopted in the paper. In the future we plan on incorporating these models in the Search facilities .
Levenhagen et al. (2017)
A Grid of Synthetic Spectra for Hot DA White Dwarfs and Its Application in Stellar Population Synthesis
In this work we present a grid of LTE and non-LTE synthetic spectra of hot DA white dwarfs. It covers 17,000 K <= Teff <= 100,000 K and 7.0 <= log g <= 9.5. The stellar models are built for pure hydrogen and the spectra cover a wavelength range from 90 nm to 2.5 micron.
In Dec 2021, we updated the models for the stars in the temperature range 17kK - 34 kK, now evaluated in a strict non-LTE regime. This new grid supersedes the previous calculations, which were built with the simplifying assumption of detailed radiative balance for cooler stars. Details of these new computations can be found here. The old models are kept in a folder named legacy.
The models in binary table FITS format can be accessed in this link. The files in ASC format can be accessed in the Vizier link. In the future we plan on incorporating these models in the Search facilities .
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 10 μm at a wavelength sampling of ∆logλ ≅ 8×10−4. Exact dispersion information can be obtained from the FITS header (air wavelength, angstrom): log10(wavelength) = CRVAL1 + CDELT1 * pixel
» 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).
» 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).
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 models cover 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
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.
Alternative downloads at: MPA Data Archive
Spanish Virtual Observatory.
Alternative downloads at:
Stellar population models
Coelho, Bruzual & Charlot (2020)
To use or not to use synthetic stellar spectra in population synthesis models?
In this work we build a synthetic stellar library - SynCoMiL (Synthetic Counterpart to the MILES Library) - mimicking the coverage of an empirical library, and Stellar Population Synthesis (SPS) models with different choices of stellar library, tailored to investigate the impact of an empirical vs. a theoretical library in simple stellar population predictions.
The models can be downloaded here. SynCoMiL is given in two files: syncomil_parameters_20191027.fits lists the atmospheric parameters used as input in the calculations, syncomil_fluxes_20191027.fits gives the fluxes, one star per column (1st column gives the wavelength). SPS models are available in the subdirectories, according to the labels adopted in the paper. In the future we plan on incorporating these models in the Search facilities .
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).
rotasul.net