Contribution of Bright Extragalactic Radio Sources to Microwave Anisotropy

Abstract

We estimate the contribution of extragalactic radio sources to fluctuations in sky temperature over the range of frequencies (10-300 GHz) used for cosmic microwave background (CMB) anisotropy measurements. CMB anisotropy observations at high resolution and low frequencies are especially sensitive to this foreground. Our catalog of 2207 bright radio sources includes 758 sources with flux measurements at 90 GHz. We develop a method to extrapolate the source spectra and predict skymaps of extragalactic radio sources at instrument resolutions of 10'-10° FWHM. Our results indicate that the brightest radio sources will dominate microwave anisotropy for a wide range of resolutions and frequencies. We predict the location and flux of the brightest radio sources at each frequency, making it straightforward to develop a template for masking the pixels containing them. This masking should be sufficient to protect most CMB anisotropy observations from unacceptable radio source confusion.