Joint Bayesian analysis of large angular scale CMB temperature anomalies
  Cosmic microwave background measurements show an agreement with the
concordance cosmology model except for a few notable anomalies: Power
Suppression, the lack of large scale power in the temperature data compared to
what is expected in the concordance model, and Cosmic Hemispherical Asymmetry,
a dipolar breakdown of statistical isotropy. An expansion of the CMB covariance
in Bipolar Spherical Harmonics naturally parametrizes both these large-scale
anomalies, allowing us to perform an exhaustive, fully Bayesian joint analysis
of the power spectrum and violations of statistical isotropy up to the dipole
level. Our analysis sheds light on the scale dependence of the Cosmic
Hemispherical Asymmetry. Assuming a scale-dependent dipole modulation model
with a two-parameter power law form, we explore the posterior pdf of amplitude
$A(l = 16)$ and the power law index $\alpha$ and find the maximum a posteriori
values $A_*(l = 16) = 0.064 \pm 0.022$ and $\alpha_* = -0.92 \pm 0.22$. The
maximum a posteriori direction associated with the Cosmic Hemispherical
Asymmetry is $(l,b) = (247.8^o, -19.6^o)$ in Galactic coordinates, consistent
with previous analyses. We evaluate the Bayes factor $B_{SI-DM}$ to compare the
Cosmic Hemispherical Asymmetry model with the isotropic model. The data prefer
but do not substantially favor the anisotropic model ($B_{SI-DM}=0.4$). We
consider several priors and find that this evidence ratio is robust to prior
choice. The large-scale power suppression does not soften when jointly
inferring both the isotropic power spectrum and the parameters of the
asymmetric model, indicating no evidence that these anomalies are coupled.
