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Description of SED models

Description of spectral energy distribution (SED) models for galaxies

FTP access the basic models is here.
Exit to the home-page of the server.

Introduction

Below, we put short descriptions of the used SED models for the photometric redshifts providing by the current server. The basic models of synthetic spectra for z and redshift calculation are applied to elliptical galaxies being very often optical counterparts for the radio galaxies. In the system advance, we suppose to expand the database by other galaxy types (S0, Sa, Sb, etc.) SEDs.

The description of Pogginati's (1997) models is given at the end of this page. Despite they are not opened at this server, we stored them in this data base. In future, we plan to use them if they will be developed.

PEGASE

The model PEGASE: Project de'Etude des Galaxies par Synthese Evolutive (Fioc and Rocca-Volmerange, 1997) for the Hubble sequence galaxies, both with star formation and evolved, was used as a basic SED (Spectral Energy Distribution) model. The uniqueness of this model consists in expanding to the near IR (NIR) of Rocca-Volmerange and Guiderdoni's (1988) atlas of synthetic spectra with a revised stellar library, which includes parameters of cool stars. The NIR is connected coherently with the visible and ultraviolet ranges, so the model is continuous and spans a range from 220 Angstrom to 5 microns. The precise algorithm of the model, to quote the authors, allows revealing rapid evolutionary phases such as red supergiants or AGB in the NIR.

We use from this model a wide collection of SED curves from the range of ages between 7x10⁶ and 19x10⁹ years for massive elliptical galaxies.

In 2001, a new improved version PEGASE.2 by Damien Le Borgne and Brigitte Rocca-Volmerange, 2001, ( astro-ph/0202359 ) was appeared. It has a corresponding server, allowing a user to operate with simulated data. We plan to use these new models of standard galaxy types too when estimation of parameters.

GISSEL

We use from the GISSEL'98 a library of synthetic spectra of galaxies from the paper of Bolzonella, Miralles и Pello (BMP, 2000). This model including 200 tracks of ages from 200 mln. up to 16 billion years for elliptical galaxies is constructed with evolutionary models of Bruzual and Charlot (1993, 1996) and corresponds approximately to observational characteristics of objects.

The library of synthetic spectra of E-galaxies is formed with the following parameters of star formation rate (SFR): simple stellar population, burst of star formation lasting is 1 billion years, exponential decreasing of SFR (mu-model), solar metallicity. Initial mass function (IMF) with an upper limit of 125 M_sun is taken from Miller and Scalo (1979), and as BMP shown in comparison with other IMFs, photometric $z$ estimations are approximately the same for different IMF choice . The model tracks cover the wavelength range from 220 up to 95800 Angstrom, but the default range is specified by redshifts in limits of z from 0 up to 6.

(Homepage of the GISSEL model).

GALEV2

This library is from the paper "Chemically consistent evolution of galaxies: II. Spectrophotometric evolution from zero to high redshift" by Jens Bicker, Uta Fritze, Claudia S. Muller, Klaus J. Fricke (Universitaetssternwarte Goettingen). ( astro-ph/0309688 ) All data are available for following galaxy types: E, Sa, Sb, Sc, and Sd (GALEV). The e and k- corrections and the apparent magnitudes (VEGAMAG system) are given for the Johnson-Cousins-Bessell and Brett U, B, V, Rc, Ic, J, H, K passbands and for the HST/WFPC2 wide-band passbands up to a redshift of z=5. The spectra are given as a function of redshift and as a function of evolution time in the restframe. In case of the redshift evolution the k-correction and the spectra are given with and without the effect of attenuation. For the cosmology it is assumed H0=65, Omega0=0.1 and a formation of galaxies at z=5. The fluxes of the spectra are given in [erg cm^-2 s^-1 A^-1]

Files can be found here.

HyperZ

One can use a system HyperZ (Bolzonella et al., 2000) for calculation of galaxy metallicity for various tracks. This system contains a library of templates of GISSEL'98 spectra. Besides, one can use a data base including of the software and filter transmissions.

The input data are: a photometric catalogue, containing magnitudes and photometric errors, and the corresponding set of filter responses (+ detector if needed). The output data are chosen by the user: best _phot, observed SEDs (mean fluxes and errors), best-fit integrated SEDs and spectra, minimum chi² versus z and possible secondary solutions. The present library of templates has been obtained from the GISSEL98 code (see details in section 4), solar metallicity (new corrected tracks), and Miller and Scalo IMF (toul_62_mi_sc_ssp), plus 4 templates taken from Coleman, Wu and Weedman (1980) and extended in the UV and IR regions with the GISSEL spectra corresponding to the same spectral type. This set of templates can be changed by the user; some specific SEDs should be available in the next version.

Poggianti's model

Another model used earlier is the model of synthetic spectra of Poggianti (1997). Because it contains only few tracks, we do not open it for a general use before new data will appear.

This model is based on the calculations including stellar component emission from Barabaro and Olivi (1991), which synthesize SED for galaxies in the spectral range from 1000 up to 10000 Angstrom and includes besides the helium burning phase phases of AGB and post-AGB stellar evolution. The model takes into account chemical evolution in galaxy, therefore, a contribution of different metallicity stellar population to the integral spectrum too. Using model of stellar atmospheres (Kurutz, 1992) Poggianti calculates a spectrum up to 25 000 Angstrom. The Kurutz's model of stars with T_eff>5500K is used for the IR range, and observed stellar spectrum library for low effective temperatures (Lancon and Rocca-Volmerange, 1992).

We use SED templates of this model, calculated for elliptical galaxies for various ages of 2.2, 3.4, 4.3, 5.9, 7.4, 8.7, 10.6, 13,2 and 15 x10⁹ years.

Литература

Barabaro S., Olivi F.M., 1991, AJ, 101, 922

Bruzual G., Charlot S. 1993, ApJ, 405, 538

Bruzual G., Charlot S. 1996, anonymous@ ftp://gemini.tuc.noao.edu/pub/charlot/bc96

Bolzonella M., Miralles J.-M., Pello R. 2000. Astron. Astroph., 363, 476. astro-ph/0003380.

Coleman D.J., Wu C.C., Weedman D.W., 1980, ApJ, 43, 393

Fioc M., Rocca-Volmerange B, 1997, AA, 326, 950

Kurutz R., 1992, in ``The stellar population of Galaxies'', IAU Symp. No 149, ed. Barbuy B.,Penzini A., Kluwer, Dordrecht, 225

Lancon A., Rocca-Volmerange B., 1992, AAS, 96, 593.

Miller G.E., Scalo J.M. 1979, ApJS, 41, 513

Poggianti B.M., 1997, AA, 122, 399

Rocca-Volmerange B., Guiderdoni B., 1988, AAS, 75, 93