Fluctuations of differential number counts of radio continuum sources
  We investigate the differential number counts of sources in radio continuum
surveys, including all terms at linear order in cosmological perturbations. Our
framework does not assume a specific gauge condition. This general approach
allows us to recover gauge invariance explicitly. With the complete derivations
of the covariant volume integral on the past light cone, we have identified
several contributions in the number counts. To clarify their underlying
physics, we present each contributions in terms of scalar, vector and tensor
modes. This theoretical framework promises to be widely applicable to continuum
radio galaxy surveys to model the expected angular power spectrum and two-point
correlation.
