We apply the dynamical modeling approach of Statler ( \markcite Statler1994b1994b ) to 13 elliptical galaxies from the Davies and Birkinshaw ( \markcite DB19881988 ) sample of radio galaxies to derive constraints on their intrinsic shapes and orientations .
We develop an iterative Bayesian algorithm to combine these results to estimate the parent shape distribution from which the sample was drawn , under the assumption that this parent distribution has no preferred orientation .
In the process we obtain improved estimates for the shapes of individual objects .
The parent shape distribution shows a tendency toward bimodality , with peaks at the oblate and prolate limits .
Under minimal assumptions about the galaxies ’ internal dynamics , 35 % of the objects would be strongly triaxial ( 0.2 < T < 0.8 ) .
However , the parent distribution is sensitive to the assumed orbit populations in the galaxies .
Dynamical configurations in which all galaxies rotate purely about either their long or short axes can be ruled out because they would require the sample to have a strong orientation bias .
Configurations in which the mean motion about the short or long axis is either “ disklike ” —dropping off away from the symmetry planes—or “ spheroidlike ” —remaining roughly constant at a given radius—are equally viable .
Spheroidlike rotation in the long-axis or short-axis tube orbits significantly lowers the abundance of prolate or oblate galaxies , respectively .
If rotation in ellipticals is generally disklike , then triaxiality is rare ; if spheroidlike , triaxiality is common .