Future Constraints on Angle-Dependent Non-Gaussianity from Large Radio
  Surveys
  We investigate how well future large-scale radio surveys could measure
different shapes of primordial non-Gaussianity; in particular we focus on
angle-dependent non-Gaussianity arising from primordial anisotropic sources,
whose bispectrum has an angle dependence between the three wavevectors that is
characterized by Legendre polynomials $\mathcal{P}_L$ and expansion
coefficients $c_L$. We provide forecasts for measurements of galaxy power
spectrum, finding that Large-Scale Structure (LSS) data could allow
measurements of primordial non-Gaussianity competitive or improving upon
current constraints set by CMB experiments, for all the shapes considered. We
argue that the best constraints will come from the possibility to assign
redshift information to radio galaxy surveys, and investigate a few possible
scenarios for the EMU and SKA surveys. A realistic (futuristic) modeling could
provide constraints of $f_{\rm NL}^{\rm loc} \approx 1 (0.5)$ for the local
shape, $f_{\rm NL}$ of $\mathcal{O}(10) (\mathcal{O}(1))$ for the orthogonal,
equilateral and folded shapes, and $c_{L=1} \approx 80 (2)$, $c_{L=2} \approx
400 (10)$ for angle-dependent non-Gaussianity. The more futuristic forecasts
show the potential of LSS analyses to considerably improve current constraints
on non-Gaussianity, and so on models of the primordial Universe. Finally, we
find the minimum requirements that would be needed to reach
$\sigma(c_{L=1})=10$, which can be considered as a typical (lower) value
predicted by some (inflationary) models.
