Measurements of anisotropy in the cosmic microwave background radiation at 0.5 deg angular scales near the star gamma ursae minoris

Abstract

We present results from a four frequency observation of a 6° x 0°.6 strip of the sky centered near the star Gamma Ursae Minoris during the fourth flight of the Millimeter-wave Anisotropy eXperiment (MAX). The observation was made with a 1°.4 peak-to-peak sinusoidal chop in all bands. The FWHM beam sizes were 0°.55 ± 0°.05 at 3.5 cm -1 and 0°.75 ± 0°.05 at 6, 9, and 14 cm -1 . During this observation significant correlated structure was observed at 3.5, 6 and 9 cm -1 with amplitudes similar to those observed in the GUM region during the second and third flights of MAX. The frequency spectrum is consistent with CMB and inconsistent with thermal emission from interstellar dust. The extrapolated amplitudes of synchrotron and free-free emission are too small to account for the amplitude of the observed structure. If all of the structure is attributed to CMB anisotropy with a Gaussian autocorrelation function and a coherence angle of 25', then the most probable values of ∆T/T CMB in the 3.5, 6, and 9 cm -1 bands are 4.3 −1.6 +2.7 × 10 −5 , 2.8 −1.1 +4.3 × 10 −5 , and 3.5 −1.6 +3.0 × 10 −5 (95% confidence upper and lower limits), respectively.

A Measurement of the Angular Power Spectrum of the Anisotropy in the Cosmic Microwave Background

“…The discovery of the anisotropy in the cosmic microwave background (CMB) by the COBE satellite (Smoot et al 1992;Bennet et al 1992) and its subsequent confirmation (Ganga et al 1993) at large angular scales (greater than 7 • ) has been followed by positive detections of anisotropies in the microwave sky at intermediate angular scales by a number of other experiments (De Benardis et al 1994;Devlin et al 1994;Dragovan et al 1994;Gundersen et al 1995;Gutierrez et al 1995) and upper limits at smaller angular scales (Meyers, Readhead, & Lawrence 1993;Tucker et al 1993). In order to reject foreground contamination, most of these experiments observe the sky over a range of frequencies.…”

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

“…Constrained by the measured level of anisotropy on large angular scales (Bennett et al 1994, Ganga et al 1993, different models predict varying levels of anisotropy on smaller scales. Several observing teams (Cheng et al 1994, de Bernardis et al 1994, Devlin et al 1994, Gundersen et al 1995, Netterfield et al 1995 including our own have reported detections of anisotropy on angular scales near 1 • . Improvements in these measurements should help discriminate between the current models of large scale structure formation.…”

Millimeter/Submillimeter Search for the Sunyaev‐Zeldovich Effect in the Coma Cluster

“…The isothermal gas parameters in Coma have been determined from an analysis of ROSAT and GINGA data (Briel, Henry, and Böhringer 1992) Recent observations of the intrinsic CMB anisotropies on angular scales ∼0. • 5 (Paper I, Cheng et al 1996, Devlin et al 1994, Netterfield et al 1996 are showing ∆T /T ∼ 2 × 10 −5 . This intrinsic level represents a potentially significant contaminant to SZ observations at these angular scales because the CMB fluctuations may be comparable to the expected signal from the SZ effect.…”