A Measurement of the Angular Power Spectrum of the Cosmic Microwave Background from [CLC][ITAL]l[/ITAL][/CLC] = 100 to 400

Abstract

We report on a measurement of the angular spectrum of the CMB between $lapprox 100$ and $lapprox 400$ made at 144 GHz from Cerro Toco in the Chilean altiplano. When the new data are combined with previous data at 30 and 40 GHz, taken with the same instrument observing the same section of sky, we find: 1) a rise in the angular spectrum to a maximum with $delta T_l approx 85~mu$K at $lapprox 200$ and a fall at $l>300$, thereby localizing the peak near $lapprox 200$; and 2) that the anisotropy at $lapprox 200$ has the spectrum of the CMB.Comment: 4 pages, 2 figures. Revised version; includes Ned Wright's postscript fix. Accepted by ApJL. Website at http://physics.princeton.edu/~cmb