Detection of features in the large-scale galaxy distribution from wide-angle samples of objective-prism spectra

Abstract

We demonstrate a promising new application of objective-prism spectra for the investigation of the large-scale distribution of galaxies. The method is based on the fact that galaxies with identifiable 4000A features on objective-prism plates are predominantly ellipticals and that such galaxies appear to delineate structure and dumpiness in the galaxy distribution. This property is particularly striking when large samples of objective-prism spectra are considered. Results from a whole plate sample presented here reveal substantial structure in the particular field studied. The potential of this technique is that large-scale structure in the galaxy distribution may be highlighted and traced across many adjacent fields and to depths of -400 h^-1 Mpc by virtue of redshifts provided by the 4000Å features. This can be done without the need for excessive amounts of observing time on large telescopes. The method should prove an important extra tool for observational cosmology.