Astron. Astrophys. 337, 699-710 (1998)

Combined population and evolutionary synthesis of galaxy spectra

A. Goerdt and W. Kollatschny

Universitäts-Sternwarte Göttingen, Geismarlandstraße 11, D-37083 Göttingen, Germany

Received 29 January 1998 / Accepted 26 June 1998

Abstract

We present our numerical code to perform syntheses of galaxy spectra. Our modified linear simplex algorithm has the advantage that no initial solution is required, the non-negativity for the individual contributions is guaranteed, additional spectral components can be added and individual wavelength regions can be weighted. Synthesizing the observed galaxy spectra with isochrone spectra we determine the age distribution of the stellar component. We demonstrate the accuracy of our method to reconstruct the age distribution of theoretical spectra. Finally, we present evolutionary syntheses of the optical spectra of an elliptical galaxy and of the spatially resolved Seyfert galaxy NGC 1365.

Key words: galaxies: stellar content galaxies: evolution galaxies: individual: NGC 1365 galaxies: Seyfert

Send offprint requests to: W. Kollatschny

SIMBAD Objects

Contents

• 1. Introduction
• 2. Synthesis procedure
  • 2.1. General linear programming technique
  • 2.2. Modified simplex algorithm
• 3. Stellar libraries
  • 3.1. Gunn & Stryker library
  • 3.2. Jacoby, Hunter & Christian library
  • 3.3. Silva & Cornell library
  • 3.4. Kurucz library
  • 3.5. Additional spectral components
    • 3.5.1. Non-thermal continuum component
    • 3.5.2. Balmer continuum, FeII quasi continuum
• 4. Isochrone spectra
  • 4.1. Synthetic isochrone spectra
    • 4.1.1. Synthetic isochrone spectra from observed stellar libraries
    • 4.1.2. Synthetic isochrone spectra from theoretical Kurucz spectra
    • 4.1.3. Comparison of synthetic isochrone spectra
• 5. Dust extinction
• 6. Metallicity
• 7. Galaxy spectra
  • 7.1. Tests of synthetic galaxy spectra
  • 7.2. Spectral synthesis of the elliptical galaxy NGC 4476
  • 7.3. Spectral synthesis of the Seyfert galaxy NGC 1365
• 8. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: August 27, 1998
helpdesk.link@springer.de