0318-The radio source counts at 15 GHz and their implications for cm-wave CMB imaging

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The radio source counts at 15 GHz and their implications for cm-wave CMB imaging Taylor 2001

Since sources are randomly distributed on the sky, the power spectrum of point sources also increases as $\ell^2$.

The removal of foreground sources, however, is not trivial. They are known to have a wide range of spectral indices.

Theoretical predictions of the extragalactic source counts at a wide range of frequencies have also been made (Toffolatti et al. 1998), but observations at relevant frequencies are still needed to confirm the results. Furthermore, although source counts enable one to predict the point-source contribution to a measured CMB power spectrum, this is helpful only if the source contribution is small compared with the CMB power. In general, finding the sources with high-resolution imaging is necessary

Sparse point-source removal for full-sky CMB experiments: application to WMAP 9-year data sureau 2014

Radio sources in next-generation CMB surveys

The first direct counts in polarization will be obtained, enabling a solid assessment of the extra-galactic source contamination of CMB maps and allowing us to understand struc-ture and intensity of magnetic fields, particle densities and structures of emitting regions close to the base of the jet.

The overwhelming majority of extragalactic radio sources detectable in the frequency range of CMB experiments are blazars, i.e. sources whose radio emission is dominated by relativistic jets collimated by intense magnetic fields and closely aligned with the line of sight. These objects with extreme properties are of special interest since they are also strong $\gamma$ ray sources: about 90% of the firmly identified extragalactic $\gamma$ ray sources are blazars.

One example of transient phenomena are outbursts from AGNs and especially from blazars. Outbursts and, more generally, variability, provide key information on the flow of the plasma within the relativistic jets. Signatures of evolving shocks in the strongest radio flares were seen by Planck Collaboration Int. XLV (2016), although much of the high frequency variability may be better approximated by achromatic variations. These results are compatible with the standard shocked jet model, but other interpretations are possible. Definite conclusions on all the above issues are currently hampered by the limited statistics. This limit will be overcome by next generation CMB experiments from space which will provide multi-epoch simultaneous observations of large blazar samples over a broad frequency range. This will allow us to study their variability properties as a function of flux density and spectral shape.

Accurate simulations (Remazeilles et al. 2018) showed that, for tensor-to-scalar ratios r ~10-3, the overall uncertainty on r is dominated by foreground residuals and that unresolved polarized point sources can be the dominant foreground contaminant over a broad range of angular scales.On the other side, polarization observations enable us to understand geometrical structure and intensity of magnetic fields, particle densities and structures of emission regions.