Resolved observations at 31 GHz of spinning dust emissivity variations
  in $\rho$ Oph
  The $\rho$ Oph molecular cloud is one of the best examples of spinning dust
emission, first detected by the Cosmic Background Imager (CBI). Here we present
4.5 arcmin observations with CBI 2 that confirm 31 GHz emission from $\rho$ Oph
W, the PDR exposed to B-type star HD 147889, and highlight the absence of
signal from S1, the brightest IR nebula in the complex. In order to quantify an
association with dust-related emission mechanisms, we calculated correlations
at different angular resolutions between the 31 GHz map and proxies for the
column density of IR emitters, dust radiance and optical depth templates. We
found that the 31 GHz emission correlates best with the PAH column density
tracers, while the correlation with the dust radiance improves when considering
emission that is more extended (from the shorter baselines), suggesting that
the angular resolution of the observations affects the correlation results. A
proxy for the spinning dust emissivity reveals large variations within the
complex, with a dynamic range of 25 at 3$\sigma$ and a variation by a factor of
at least 23, at 3$\sigma$, between the peak in $\rho$ Oph W and the location of
S1, which means that environmental factors are responsible for boosting
spinning dust emissivities locally.
