View article

We report measurements of anisotropy in the cosmic microwave background radiation over the multipole range l∼ 200–3500 with the Cosmic Background Imager based on deep observations of three fields. These results confirm the drop in power with increasing l first reported in earlier measurements with this instrument and extend the observations of this decline in power out to l∼ 2000. The decline in power is consistent with the predicted damping of primary anisotropies. At larger multipoles, l= 2000–3500, the power is 3.1 σ greater than standard models for intrinsic microwave background anisotropy in this multipole range and 3.5 σ greater than zero. This excess power is not consistent with expected levels of residual radio source contamination but, for σ 8≳ 1, is consistent with predicted levels of a secondary Sunyaev-Zeldovich anisotropy. Further observations are necessary to confirm the level of this excess …