  We report on a combined experimental and theoretical study of polarization
self-rotation in an ultracold atomic sample. In the experiments, a probe laser
is tuned in the spectral vicinity of the D1 line to observe polarization
self-rotation in a sample of ultracold Rb prepared in a magneto-optical trap.
Systematic measurements of the rotation angle of the light-polarization ellipse
as a function of laser intensity, initial ellipticity and detuning are made.
The observations, in good agreement with theoretical simulations, are
indicative of the presence of a residual static magnetic field, resulting in
measured asymmetries in the rotation angle for right and left ellipticities. In
this paper we present our detailed experimental results and analysis of the
combined influences of polarization self-rotation and the Faraday effect.
