EPSS - 2 D : a fast computer code for simulating all – sky maps of clustered extragalactic point sources

We present a fast computer code based on a simple algorithm for simulating realistic 2D distributions of clustered extragalactic point sources (EPS) in flat patches of the sky as well as in the whole sky. By this method we are able to provide new predictions on the angular power spectrum of cosmic microwave background (CMB) fluctuations due to undetected EPS which improve on previous ones. Both radio and far–IR selected source populations are taken into account. To analyze different clustering scenarios, we exploit angular power spectra of EPS, 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 cm wavelengths – we are able to reproduce current data on the two–point angular correlation functions of sources, w(θ), and we can confirm that the detection of primordial CMB anisotropies is not hampered by 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 – 2 – of intrinsic CMB anisotropies, thus confirming previous theoretical predictions. Moreover, we show that the clustering of EPS could not be ruled out as an explanation of the excess signal detected at high multipoles by recent CMB anisotropy experiments. As a final result, we also present an example of a currently feasible realistic map of EPS, by taking into account data on bright sources as well as the Toffolatti et al. model. Moreover, these simulated sky maps can prove very useful to test the efficiency of component separation techniques, the capability of new algorithms for the detection of EPS and the appearance of non Gaussian signatures in " residue " CMB maps, in the presence of sources which are not Poisson distributed in the sky.