Engineering topics
Publications and source records attributed to Potter, M. D..
It is still not known whether elliptical galaxies are oblate, prolate or triaxial. The prototype prolate galaxy NGC2685 has a rapid observed stellar rotation rate around the projected minor axis. It is shown that a steady figure, exactly prolate model can have no such rotation, and that a nearly prolate model fails by a factor of 7. The galaxy is suggested to be oblate with gas disk that is the wreck of a dwarf companion.
Galactic mass loss due to gas production by an evolving stellar population and removal due to supernovae or some other energy source can alter the size of a galaxy over a long time through the adiabatic invariants of the orbits. Numerical and analytic results show that if the mass profile changes homologously, the scale size of the galaxy does also. Under conventional assumptions about galaxy age and initial mass function, this bloating is smaller than the differences between open and flat cosmologies at z = 0.5. If, however, some elliptical galaxies maintain star formation until recent epochs and then lose a (correspondingly) larger fraction of their mass, the effect may be important. It may also be important in decreasing the size of cD galaxies as a result of gas accretion.