C-Band All-Sky Survey: A First Look at the Galaxy
  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.
