Constraints on the High-ell Power Spectrum of Millimeter-Wave Anisotropies from APEX-SZ

We present measurements of the angular power spectrum of millimeter wave anisotropies with the APEX-SZ instrument. APEX-SZ has mapped 0.8 deg² of sky at a frequency of 150 GHz with an angular resolution of 1'. These new measurements significantly improve the constraints on anisotropy power at 150 GHz over the range of angular multipoles 3000 < ell < 10, 000, limiting the total astronomical signal in a flat band power to be less than 105 μK² at 95% CL. We expect both submillimeter-bright, dusty galaxies and to a lesser extent secondary cosmic microwave background anisotropies from the Sunyaev-Zel'dovich effect (SZE) to significantly contribute to the observed power. Subtracting the SZE power spectrum expected for σ₈ = 0.8 and masking bright sources, the best-fit value for the remaining power is C _ell = 1.1^+0.9 _-0.8 × 10^-5 μK² (1.7^+1.4 _-1.3 Jy² sr^-1). This agrees well with model predictions for power due to submillimeter-bright, dusty galaxies. Comparing this power to the power detected by BLAST at 600 GHz, we find the frequency dependence of the source fluxes to be S_ν ∝ ν^{2.6^{+0.4}_{-0.2}} if both experiments measure the same population of sources. Simultaneously fitting for the amplitude of the SZE power spectrum and a Poisson-distributed point source population, we place an upper limit on the matter fluctuation amplitude of σ₈ < 1.18 at 95% confidence.