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 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.

16 pages, 9 figures, submitted to MNRAS, referee's corrections made, awaiting for final approval for publication

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Cited by in corpus (8)

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• QUIJOTE scientific results -- X. Spatial variations of Anomalous Microwave Emission along the Galactic plane
• QUIJOTE scientific results -- V. The microwave intensity and polarisation spectra of the Galactic regions W49, W51 and IC443
• QUIJOTE scientific results -- XVIII. New constraints on the polarization of the Anomalous Microwave Emission in bright Galactic regions: $\rho$\,Ophiuchi, Perseus and W43
• A new look at the integrated radio/microwave continuum spectrum of Galactic supernova remnant IC443
• A global view on star formation: The GLOSTAR Galactic plane survey XII. Effelsberg's continuum view and data release