  Correlations of azimuthal angles observed at RHIC have gained great attention
due to the prospect of identifying fluctuations of parity-odd regions in the
field sector of QCD. Whereas the observable of interest related to parity
fluctuations involves subtracting opposite-sign from same-sign correlations,
the STAR collaboration reported the same-sign and opposite-sign correlations
separately. It is shown here how momentum conservation combined with collective
elliptic flow contributes significantly to this class of correlations, though
not to the difference between the opposite- and same-sign observables. The
effects are modeled with a crude simulation of a pion gas. Though the
simulation reproduces the scale of the correlation, the centrality dependence
is found to be sufficiently different in character to suggest additional
considerations beyond those present in the pion gas simulation presented here.
