On the Deprojection of Axisymmetric and Triaxial Stellar Systems

Abstract

The deprojection problem for transparent stellar systems is discussed. An axisymmetric model galaxy can be made disky or boxy without altering its projected image by adding a ‘konus density’. The range of invisible konus densities increases as the inclination of the galaxy decreases from edge-on to face-on.

The deprojection of triaxial systems is indeterminate not only because of the well-known global changes of the axial ratios and viewing angles which leave the image unchanged. There also exist seven families of ‘funnel densities’ corresponding to invisible disky or boxy structures with respect to the three principal planes and four other, inclined planes. In the triaxial case, the uncertainties in the deprojection are important for all projection directions.