Template ultraviolet to near-infrared spectra of star-forming galaxies and their application to K-corrections

Abstract

Template UV-optical spectra of quiescent and starburst galaxies are presented and used to derive K­ corrections as a function of morphological type and redshift. IUE observations and archival data are used for the UV template spectra. The optical spectra are from ground-based observations obtained in apertures that match closely the 200 arcsec² IUE aperture. The templates of quiescent galaxies are built according to morphological type, elliptical, bulge, SO, Sa, Sb, and Se, and the templates of starburst gal­ axies according to color excess. The unprecedented characteristics of these templates is that UV and optical spectra have been obtained in matched apertures to produce consistent spectral information from 1200 to 10,000 Å Despite the relatively small IUE aperture, the galaxy stellar populations are well represented in the elliptical, SO, Sa, and Se, and in the starburst templates. The spectra are available digitally. The UV-optical templates can be applied to the classification of high-redshift galaxies and to the iden­ tification of the host galaxies of quasars. The templates predict that observed magnitudes from traditional ground-based photometric surveys can be uniquely interpreted. For example, U, B, and I magnitudes uniquely determine both the redshift and the morphological type of a galaxy. The template spectra are also used to calculate K-corrections for galaxies as a function of morphological type and redshift, up to z = 2. These improved K-corrections are not sufficient to explain the excess counts in faint blue galaxies. A subset of our galaxy templates are linked with published data from the radio to the X-ray for gal­ axies and quasars. A comparison between the quiescent galaxies and the quasars suggests that, in the optical band, the host galaxy is a factor of 10-100 fainter in flux than the quasar.