Anisotropy in the Microwave Sky at 90 GH[CLC]z[/CLC]: Results from Python III

The third year of observations with the Python microwave backgroundexperiment densely sample a $5.5^o\times 22^o$ region of sky that includes thefields measured during the first two years of observations with thisinstrument. The sky is sampled in two multipole bands centered at $l \approx92$ and $l \approx 177$. These two data sets are analyzed to place limits onfluctuations in the microwave sky at 90 GHz. Interpreting the observedfluctuations as anisotropy in the cosmic microwave background we find flat bandpower estimates of $\delta T_l\equiv \sqrt{l(l+1)C_l/2\pi }% =54_{-12}^{+14}\muK$ at $l=92_{-24}^{+37}$ and $\delta T_l=58_{-13}^{+15}\mu K$ at$l=177_{-58}^{+66}$. Combining the entire three year set of Pythonobservations, we find that the angular power spectrum of fluctuations has aspectral index $m=.02_{-.16}^{+.18}$ and an amplitude $% \deltaT_{l_e}=53_{-11}^{+13}\mu K$ at $l_e=145_{-74}^{+59}$ for the functional form$\delta T_l=\delta T_{l_e}(l/l_e)^m$. The stated uncertainties in theamplitudes and spectral index represent 1$\sigma $ confidence intervals in thelikelihood added in quadrature with a 20\% calibration uncertainty and anestimate of the effects introduced due to imperfect overlap of the beams on thesky. The limits of $l$ are determined from the full width at half maximum ofthe window functions.Comment: 16 pages, postscript, 2 figure