Suppression of gravitational structure formation by cosmological accretionheating

As increasingly precise information about the spectrum of the cosmic microw ave background fluctuations is gathered with balloon and satellite experime nts, interest has grown in foreground sources of opacity affecting these ob servations. One potentially important source is electron scattering produce d by postrecombination luminosity, 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 suppr essing early gravitational structure formation. Here we consider the effect s of such heating. We concentrate on one type of ionization source: luminos ity generated by accretion onto primordial compact objects. We show that if such objects generate enough luminosity to affect the cosmic microwave bac kground power spectrum, then they would produce enough heat to prevent the formation of 1 sigma collapsed objects until z similar to 5, significantly less than the redshift at which baryonic collapse could otherwise occur. Su ch processes would leave signatures detectable by upcoming instruments such as the Next Generation Space Telescope, the SIRTF, and Swift.