| Name: | Akashdeep Karan |
| Affiliation: | Indian Institute of Science Education and Research Tirupati |
| Conference ID : | ASI2024_194 |
| Title : | Analyzing statistical isotropy violation due to non-circular beam in real space |
| Authors : | Akashdeep Karan1, Dipanshu Garg23, Tarun Souradeep234 |
| Authors Affiliation: | 1 Department of Physics, Indian Institute of Science Education and Research, Tirupati 517507 India
2 Department of Physics, Indian Institute of Science Education and Research, Pune 411008, India
3 Raman Research Institute, Bangalore 560080, India
4 Inter University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune-411007, India |
| Mode of Presentation: | Poster |
| Abstract Category : | Galaxies and Cosmology |
| Abstract : | From the fundamental assumptions of cosmology, we expect the Cosmic Microwave Background(CMB) map to be Gaussian and Statistically Isotropic(SI). However, the observations from recent experiments differed from our expectations. Deviation from the assumption of SI in the CMB map can be attributed to different physical anomalies and observational artifacts. Cosmic topology, Doppler boost, and weak lensing are some physical sources for breakdown of SI. Whereas, observational artifacts include beam non-circularity, foreground residuals, masking effect, etc. Non-circular (NC) beam effect is one of the most discussed systematic SI violation sources in the post-WMAP era of CMB anisotropy analysis. The CMB map we observe is a convolution of the underlying CMB signal with the instrumental beam response function. Although the beam response is expected to be circular around the pointing direction, any real beam function will have a deviation from circular symmetry. The NC Beam, coupled with the scanning strategy, causes complex signal modification and, consequently, severe contamination in SI measurements. It poses a tough challenge to separate the NC beam effect and obtain the actual underlying signal for studying the SI violations. Hence, it is important to quantify this effect with a proper mathematical formalism. In general, any SI violation can be parameterized by decomposing the two-point correlation function of the CMB map in the Bipolar Spherical Harmonic (BipoSH) basis. The BipoSH basis has been successful in quantifying the NC Beam effect in harmonic space. In this work, we adopt a reduction of BipoSH functions, known as minimal Harmonics. This reduction technique gives rise to a new generalized set of angular correlation functions - mBipoSH. The conversion into mBipoSH allows us to study non-SI features in real (theta) space rather than spherical harmonic space. |
