Linear Dimensions and True Axial Ratios of Galaxies

Linear diameters require knowledge of both the apparent diameters and the true distance. Apparent diameters are not uniquelly well defined, and distances are still generally quite uncertain. The standard compilation of diameters defined ata a variety of isophotes is [RC3]. Redshifts combined with an adopted Hubble constant can be used to derive distances for galaxies well beyond (> 2-3,000 km/sec, say) the obvious perturbations of nearby clusters (e.g., Virgo).

It has been demonstrated [Sand70] that the observed distribution of axial ratios for elliptical galaxies could result from an intrinsic distribution R(a) where the R(a) = 0.0 for 0 < a < 0.3 and R(a) = 1.0 elsewhere, or from an intrinsic Gaussian distribution with a mean ellipticity < a > = 0.65 and ~ 0.2.