Correlating galaxy morphologies and spectra in the 2dFGRS

Abstract

The correlation between a galaxy's morphology and its observed optical spectrum is investigated. As an example, 4000 galaxies from the 2dF Galaxy Redshift Survey, which possess both good quality spectra and have visually determined morphologies are analysed. Of particular use is the separation of Early and Late type galaxies present in a redshift survey since these can then be used in their respective redshift-independent distance estimators (Dn-sigma and Tully-Fisher). It is determined that galaxies in this sample can be relatively successfully separated into these two types by the use of various statistical methods. These methods are briefly outlined in this paper and are also compared to the default 2dFGRS spectral classification (eta). In addition it is found that the 4000Ang break in the spectrum is the best discriminant in determining its morphological type.