PREDICTIONS OF THE ANGULAR POWER SPECTRUM OF CLUSTERED EXTRAGALACTIC POINT SOURCES AT COSMIC MICROWAVE BACKGROUND FREQUENCIES FROM FLAT AND ALL-SKY TWO-DIMENSIONAL SIMULATIONS

摘要

We present predictions of the angular power spectrum of cosmic microwave background (CMB) fluctuations due to extragalactic point sources (EPSs) by using a method for simulating realistic two-dimensional distributions of clustered EPSs. Both radio- and far-IR-selected source populations are taken into account. To analyze different clustering scenarios, we exploit the angular power spectra of EPSs, P(k), estimated either by data coming from currently available surveys or by means of theoretical predictions. By adopting the source number counts predicted by the Toffolatti et al. evolution model, capable of accounting well for the available data at radio (centimeter) wavelengths, we are able to reproduce current data on the two-point angular correlation functions, w(θ), of radio sources. We can confirm that the detection of primordial CMB anisotropies is not hampered by undetected clustered sources at frequencies ≤ 150-200 GHz. On the other hand, our current findings show that at higher frequencies the clustering signal could severely reduce the detectability of intrinsic CMB anisotropies, thus confirming previous theoretical predictions. We also show that unsubtracted EPSs can account for the excess signal at high multipoles detected by recent CMB anisotropy experiments. Moreover, the additional power due to the clustering of sources gives rise to a small but nonnegligible contribution to the same excess signal. As a final result, we also present an example of a currently feasible realistic map of EPSs at 70 GHz, by taking into account data on bright detected . sources, as well as the previously quoted model for number counts. Eventually, these simulated sky maps could prove very useful for testing the efficiency of component separation techniques, the capability of new algorithms for the detection of EPSs, and the appearance of non-Gaussian signatures in "residue" CMB maps, in the presence of sources that are not Poisson-distributed in the sky.