EXTRAGALACTIC SOURCE COUNTS AND CONTRIBUTIONS TO THE ANISOTROPIES OF THE COSMIC MICROWAVE BACKGROUND - PREDICTIONS FOR THE PLANCK SURVEYOR MISSION

We present predictions for the counts of extragalactic sources, the co ntributions to fluctuations and their angular power spectrum in each c hannel foreseen for the Planck Surveyor (formerly COBRAS/SAMBA) missio n. The contribution to fluctuations owing to clustering of both radio and far-IR sources is found to be generally small in comparison with t he Poisson term; however the relative importance of the clustering con tribution increases and may eventually become dominant if sources are identified and subtracted down to faint flux limits. The central Planc k frequency bands are expected to be 'clean': at high galactic latitud e (\b\ > 20 degrees), where the reduced galactic noise does not preven t the detection of the extragalactic signal, only a tiny fraction of p ixels is found to be contaminated by discrete extragalactic sources. M oreover, the 'flat' angular power spectrum of fluctuations resulting f rom extragalactic sources substantially differs from that of primordia l fluctuations; therefore, the removal of contaminating signals is eas ed even at frequencies where point sources give a sizeable contributio n to the foreground noise.