  As increasingly precise information about the spectrum of the cosmic
microwave background fluctuations is gathered with balloon and satellite
experiments, interest has grown in foreground sources of opacity affecting
these observations. One potentially important source is electron scattering
produced by a post-recombination luminosity source, which would significantly
attenuate the higher harmonics in the spectrum. If such an ionization source
exists, then it would also heat the universe, hence increasing the Jeans mass
and suppressing early gravitational structure formation. Here we consider the
effects of such heating. We concentrate on one type of ionization source:
luminosity generated by accretion onto primordial compact objects. We show that
if such objects generate enough luminosity to affect the CMB power spectrum,
then they would produce enough heat to prevent the formation of 1 sigma
collapsed objects until redshifts of about 5, significantly less than the
redshift at which baryonic collapse could otherwise occur. Such processes would
leave signatures detectable by upcoming instruments such as NGST, SIRTF, and
SWIFT.
