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Max Tegmark, Angelica de Oliveira-Costa, John Staren, Peter Meinhold, Philip Lubin, Jeffrey Childers, Newton Figueiredo, Todd Gaier, Mark Lim, Michael Seiffert, Thyrso Villela & Carlos Alexandre Wuensche
We present Cosmic Microwave Background (CMB) maps from the Santa Barbara HACME balloon experiment (Staren etal 2000), covering about 1150 square degrees split between two regions in the northern sky, near the stars gamma Ursae Minoris and alpha Leonis, respectively. The FWHM of the beam is about 0.77 degrees in three frequency bands centered on 39, 41 and 43 GHz. The results demonstrate that the thoroughly interconnected scan strategy employed allows efficient removal of 1/f-noise and slightly variable scan-synchronous offsets. The maps display no striping, and the noise correlations are found to be virtually isotropic, decaying on an angular scale around one degree. The noise performance of the experiment resulted in an upper limit on CMB anisotropy. However, our results demonstrate that atmospheric contamination and other systematics resulting from the circular scanning strategy can be accurately controlled, and bodes well for the planned follow-up experiments BEAST and ACE, since they show that even with the overly cautious assumption that 1/f-noise and offsets will be as dominant as for HACME, the problems they pose can be readily overcome with the mapmaking algorithm discussed. Our prewhitened notch-filter algorithm for destriping and offset removal should be useful also for other balloon- and ground-based experiments whose scan strategies involve substantial interleaving.
Accepted for publication in ApJ
This figure shows a sequence of signal-to-noise eigenmodes (top row). When they are multiplied by the corresponding S/N coefficients and summed, the original map is recovered (middle row). When the terms in this sum are weighted by their signal-to-noise ration, the Wiener filtered map results (bottom row).