Abstract Details
| Name: Shabbir Shaikh Affiliation: Inter-University Centre for Astronomy and Astrophysics, Pune. Conference ID: ASI2018_618 Title : Bayesian analysis of hemispherical asymmetry observed in CMB Authors and Co-Authors : Suvodip Mukherjee (CC A, Flatiron Institute, USA), Santanu Das (University of Wisconsin-Madison, USA), Tarun Souradeep (IUCAA, Pune, India), Benjamin Wandelt (CCA, Flatiron Institute, USA) Abstract Type : Contributed Talk Abstract Category : General Relativity and Cosmology Abstract : WMAP and Planck measurements of CMB temperature anisotropies contain the anomalous signature of violation of statistical isotropy called hemispherical asymmetry. This signal is modelled as dipole modulation of otherwise statistically isotropic temperature anisotropy. Current methods in the literature estimate the significance of this signal around three sigmas. We carried out a Bayesian analysis of SMICA CMB temperature anisotropy map provided by Planck mission, taking into account the mask and inhomogeneous noise. We follow the formalism given in Santanu Das et al. JCAP 2015, where the likelihood is defined using harmonic space parameters of the dipole (m1M) in dipole modulation model. To treat the noise, we sample m1M jointly with spherical harmonic coefficients of the CMB map (alm). We use Hamiltonian Monte Carlo (HMC) method to sample the likelihood distribution of these parameters. HMC method allows efficient sampling of the multidimensional joint probability distribution of alms and m1Ms. The magnitude and the direction of the dipole we infer are in agreement with that given in the literature. We also study the aspects of the scale dependence of the hemispherical asymmetry, finding that the signal strength goes down roughly above the multipole of 64. |