AXIAL RATIOS OF EDGE-ON SPIRALS

A diameter-limited sample of 888 normal Sa-Sc galaxies was compiled from the Uppsala General Catalogue. New micrometer measures of the axial ratios R of the disc components of 262 edge-on spirals in this sample were made on copies of blue Palomar Sky Survey plates and calibrated against photometric standards. The distribution of isophotal axial ratios for the whole sample was analysed to give information on the true axial ratios R0 of spiral discs. The mean value of log R0 is 0.95 +/- 0.03 and the dispersion about this mean is 0.12 +/- 0.04. A similar mean value (0.90) was obtained from a volume-limited sub-sample of 348 spirals. The dispersion in log R0 is partly due to a dependence of R0 on morphological type, and the mean value of log R0 for each type was estimated. Inclinations of 342 edge-on (R greater-than-or-similar-to 3) spirals were determined from their isophotal axial ratios and types. No significant dependence of R0 on luminosity at each type was found.