The C-Band All-Sky survey (C-BASS)
Abstract:
The C-Band All-Sky survey (C-BASS) is an experiment to image the whole sky in intensity and polarization at 5 GHz. The primary aim of C-BASS is to provide low-frequency all-sky maps of the Galactic emission which will enable accurate component separation analysis of both existing and future CMB intensity and polarization imaging surveys. Here we present an overview of the experiment and an update on the current status of observations. We present simulation results showing the expected improvement in the recovery of CMB and foreground signals when including C-BASS data as an additional low-frequency channel, both for intensity and polarization. We also present preliminary results from the northern part of the sky survey.The C-Band All-Sky Survey (C-BASS): design and capabilities
The state-of-play of Anomalous Microwave Emission (AME) research
Abstract:
Anomalous Microwave Emission (AME) is a component of diffuse Galactic radiation observed at frequencies in the range ≈10–60 GHz. AME was first detected in 1996 and recognised as an additional component of emission in 1997. Since then, AME has been observed by a range of experiments and in a variety of environments. AME is spatially correlated with far-IR thermal dust emission but cannot be explained by synchrotron or free–free emission mechanisms, and is far in excess of the emission contributed by thermal dust emission with the powerlaw opacity consistent with the observed emission at sub-mm wavelengths. Polarization observations have shown that AME is very weakly polarized ( ≲ 1 %). The most natural explanation for AME is rotational emission from ultra-small dust grains (“spinning dust”), first postulated in 1957. Magnetic dipole radiation from thermal fluctuations in the magnetization of magnetic grain materials may also be contributing to the AME, particularly at higher frequencies ( ≳ 50 GHz). AME is also an important foreground for Cosmic Microwave Background analyses. This paper presents a review and the current state-of-play in AME research, which was discussed in an AME workshop held at ESTEC, The Netherlands, June 2016.Observations of Galactic star-forming regions with the Cosmic Background Imager at 31 GHz
C-Band All-Sky Survey: a first look at the Galaxy
Abstract:
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 tomake temperature-temperature plots, we find synchrotron spectral indices of β = -2.65 ± 0.05 between 0.408 and 5 GHz and β = -2.72 ± 0.09 between 1.420 and 5 GHz for -10° > |b| > -4°, 20° > l > 40°. Through the subtraction of a radio recombination line free-free template, we determine the synchrotron spectral index in the Galactic plane (|b|>4°) to be β =-2.56±0.07 between 0.408 and 5 GHz, with a contribution of 53±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 4.4Σ, 3.1Σ and 2.5Σ, respectively. The CORNISH (Co-Ordinated Radio 'N' Infrared Survey for High mass star formation) VLA 5-GHz source catalogue rules out the possibility that the excess emission detected around 30 GHz may be due to ultracompact HII regions. Diffuse AME was also identified at a 4Σ level within 30° > l > 40°, -2° > b > 2° between 5 and 22.8 GHz.