Far-sidelobe contamination of the Bell Laboratories H I survey

This paper describes an approximate calculation of the far-sidelobe contamination present in the Bell Laboratories H I survey. The general method is to determine the position of the sidelobe, and to assume that the emission measured at the position of the sidelobe is free of contamination. We have analyzed the errors introduced by saturation in the main beam and found them to be insignificant. The far-sidelobe contamination is shown to be less than 2 x 10 exp 16/sq cm/per km/s over most of the entire sky. The low level of far-sidelobe contamination suggests that such contamination does not affect results from studies of H I 21-cm radiation at high latitudes during the Bell Laboratories Survey. In particular, the low-column-density features of high-velocity and intermediate-velocity clouds can be deemed real.