Suppression of gravitational structure formation by cosmological accretion heating

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 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 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 cosmic microwave background power spectrum, then they would produce enough heat to prevent the formation of 1 σ collapsed objects until z ∼ 5, significantly less than the redshift at which baryonic collapse could otherwise occur. Such processes would leave signatures detectable by upcoming instruments such as the Next Generation Space Telescope, the SIRTF, and Swift.