The Temperature of the CMB at 10 GHz

TL;DR

This study measures the low-frequency spectrum of the Cosmic Microwave Background using a balloon-borne radiometer, aiming to detect deviations from a perfect blackbody spectrum that could reveal early universe processes.

Contribution

It provides new precise measurements of the CMB temperature at 10 and 30 GHz with a cryogenic balloon-borne instrument, improving constraints on spectral deviations.

Findings

CMB temperature at 10 GHz is 2.721 +/- 0.010 K

CMB temperature at 30 GHz is 2.694 +/- 0.032 K

Residuals are less than 50 mK peak-to-peak

Abstract

We report the results of an effort to measure the low frequency portion of the spectrum of the Cosmic Microwave Background Radiation (CMB), using a balloon-borne instrument called ARCADE (Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission). These measurements are to search for deviations from a thermal spectrum that are expected to exist in the CMB due to various processes in the early universe. The radiometric temperature was measured at 10 and 30 GHz using a cryogenic open-aperture instrument with no emissive windows. An external blackbody calibrator provides an in situ reference. A linear model is used to compare the radiometer output to a set of thermometers on the instrument. The unmodeled residuals are less than 50 mK peak-to-peak with a weighted RMS of 6 mK. Small corrections are made for the residual emission from the flight train, atmosphere, and foreground Galactic emission. The measured radiometric temperature of the CMB is 2.721 +/- 0.010 K at 10 GHz and 2.694 +/- 0.032 K at 30 GHz.