The correlation of X-ray and optical luminosities of early-type galaxies using new data and distances

Using new apparent magnitudes and new distances as determined from the D-n-sigma method, we have reexamined the correlation of X-ray to optical luminosities for E and S0 galaxies. The residuals about our least-squares fits decline significantly but are not removed altogether. All attempts to correlate the remaining residuals with other structural and spectral parameters have given negative results, suggesting that some other, as yet unidentified, factor plays a role in defining X-ray luminosity with respect to optical luminosity. L-x versus L-B also appears to be a useful secondary distance indicator for early-type galaxies.