We present an analysis of the diffuse emission at 5 GHz in the first quadrant of the Galactic plane using two months of preliminary intensity data taken with the C-Band All Sky Survey (C-BASS) northern instrument at the Owens Valley Radio Observatory
, California. Combining C-BASS maps with ancillary data to make temperature-temperature plots we find synchrotron spectral indices of $beta = -2.65 pm 0.05$ between 0.408 GHz and 5 GHz and $ beta = -2.72 pm 0.09$ between 1.420 GHz and 5 GHz for $-10^{circ} < |b| < -4^{circ}$, $20^{circ} < l < 40^{circ}$. Through the subtraction of a radio recombination line (RRL) free-free template we determine the synchrotron spectral index in the Galactic plane ($ |b| < 4^{circ}$) to be $beta = -2.56 pm 0.07$ between 0.408 GHz and 5 GHz, with a contribution of $53 pm 8$ per cent from free-free emission at 5,GHz. These results are consistent with previous low frequency measurements in the Galactic plane. By including C-BASS data in spectral fits we demonstrate the presence of anomalous microwave emission (AME) associated with the HII complexes W43, W44 and W47 near 30 GHz, at 4.4 sigma, 3.1 sigma and 2.5 sigma respectively. The CORNISH VLA 5 GHz source catalogue rules out the possibility that the excess emission detected around 30;GHz may be due to ultra-compact HII regions. Diffuse AME was also identified at a 4 sigma level within $30^{circ} < l < 40^{circ}$, $-2^{circ} < b < 2^{circ}$ between 5 GHz and 22.8 GHz.
We give a description of the design, construction and testing of the 30 and 44 GHz Front End Modules (FEMs) for the Low Frequency Instrument (LFI) of the Planck mission to be launched in 2009. The scientific requirements of the mission determine the
performance parameters to be met by the FEMs, including their linear polarization characteristics. The FEM design is that of a differential pseudo-correlation radiometer in which the signal from the sky is compared with a 4-K blackbody load. The Low Noise Amplifier (LNA) at the heart of the FEM is based on indium phosphide High Electron Mobility Transistors (HEMTs). The radiometer incorporates a novel phase-switch design which gives excellent amplitude and phase match across the band. The noise temperature requirements are met within the measurement errors at the two frequencies. For the most sensitive LNAs, the noise temperature at the band centre is 3 and 5 times the quantum limit at 30 and 44 GHz respectively. For some of the FEMs, the noise temperature is still falling as the ambient temperature is reduced to 20 K. Stability tests of the FEMs, including a measurement of the 1/f knee frequency, also meet mission requirements. The 30 and 44 GHz FEMs have met or bettered the mission requirements in all critical aspects. The most sensitive LNAs have reached new limits of noise temperature for HEMTs at their band centres. The FEMs have well-defined linear polarization characteristcs.
We present evidence for anomalous microwave emission in the RCW175 hii region. Motivated by 33 GHz $13arcmin$ resolution data from the Very Small Array (VSA), we observed RCW175 at 31 GHz with the Cosmic Background Imager (CBI) at a resolution of $4a
rcmin$. The region consists of two distinct components, G29.0-0.6 and G29.1-0.7, which are detected at high signal-to-noise ratio. The integrated flux density is $5.97pm0.30$ Jy at 31 GHz, in good agreement with the VSA. The 31 GHz flux density is $3.28pm0.38$ Jy ($8.6sigma$) above the expected value from optically thin free-free emission based on lower frequency radio data and thermal dust constrained by IRAS and WMAP data. Conventional emission mechanisms such as optically thick emission from ultracompact hii regions cannot easily account for this excess. We interpret the excess as evidence for electric dipole emission from small spinning dust grains, which does provide an adequate fit to the data.
