Clustering at 74 MHz

In order to construct accurate point sources simulations at the frequencies relevant to 21 cm experiments, the angular correlation of radio sources must be taken into account. Using the 74 MHz VLSS survey, we measured the angular 2-point correlation function, w(\theta). We obtain the first measurement of clustering at the low frequencies relevant to 21 cm tomography. We find that a single power law with shape w(\theta) = A \theta^{-\gamma} fits well the data. For a galactic cut of 10 degrees, with a data cut of \delta less than -10 degrees, and a flux limit of S = 770 mJy, we obtain a slope of \gamma = (-1.2 +/- 0.35). This value of \gamma is consistent with that measured from other radio catalogues at the millimeter wavelengths. The amplitude of clustering has a length of 0.2 degrees - 0.6 degrees, and it is independent of the flux-density threshold.