High sensitivity measurements of the CMB power spectrum with the extended Very Small Array

We present deep Ka-band ($\nu \approx 33$ GHz) observations of the CMB made with the extended Very Small Array. This array produces a synthesized beam width (FWHM) of $\sim 11$ arcmin and covers an $\ell$-range of 300 to 1500. On these scales, foreground extragalactic sources can be a major source of contamination to the CMB anisotropy. This problem has been alleviated by simultaneously monitoring identified sources with a separate, high resolution interferometer. The results of the source survey, with a completeness limit of 20 mJy, are then used to subtract sources directly from the VSA data. In addition, we calculate a statistical correction for the small residual contribution from weaker sources that are below the limit of the survey. The data presented have a relatively high resolution in $\ell$ compared to previous measurements at $\ell \gtsim 1000$; this is achieved by using mosaiced observations in 7 regions covering a total of approximately 82 sq. degrees. Our resolution of $\Delta \ell \approx 60$ between $\ell=300$ and $\ell = 1500$ allows the first 3 acoustic peaks to be more clearly identified. The CMB power spectrum corrected for Galactic foregrounds and extragalactic point sources is presented between $\ell=150$ and 1500. This is achieved by combining the complete extended array data with earlier VSA data in a compact configuration. There is good agreement with WMAP data up to $\ell=700$ where WMAP data run out of resolution. In the range $\ell=150-1500$ the agreement in power spectrum amplitudes with the other two sensitive experiments (ACBAR and CBI) is encouragingly close despite the differences in frequency and observing technique.