Savitribai Phule Pune University | All Models Are False, Some Are Useful |
Title | Unveiling acoustic physics of the CMB using nonparametric estimation of the temperature angular power spectrum for Planck |
Author/s |
Amir Aghamousa
Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea Arman Shafieloo Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea Department of Physics, POSTECH, Pohang, Gyeongbuk 790-784, Korea Mihir Arjunwadkar Centre for Modeling and Simulation, Savitribai Phule Pune University, Pune 411 007, India Tarun Souradeep Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganesh Khind, Pune 411 007, India |
Abstract | Estimation of the angular power spectrum is one of the important steps in Cosmic Microwave Background (CMB) data analysis. Here, we present a nonparametric estimate of the temperature angular power spectrum for the Planck 2013 CMB data. The method implemented in this work is model-independent, and allows the data, rather than the model, to dictate the fit. Since one of the main targets of our analysis is to test the consistency of the ΛCDM model with Planck 2013 data, we use the nuisance parameters associated with the best-fit ΛCDM angular power spectrum to remove foreground contributions from the data at multipoles ≥ 50. We thus obtain a combined angular power spectrum data set together with the full covariance matrix, appropriately weighted over frequency channels. Our subsequent nonparametric analysis resolves six peaks (and five dips) up to ~1850 in the temperature angular power spectrum. We present uncertainties in the peak/dip locations and heights at the 95% confidence level. We further show how these reflect the harmonicity of acoustic peaks, and can be used for acoustic scale estimation. Based on this nonparametric formalism, we found the best-fit ΛCDM model to be at 36% confidence distance from the center of the nonparametric confidence set – this is considerably larger than the confidence distance (9%) derived earlier from a similar analysis of the WMAP 7-year data. Another interesting result of our analysis is that at low multipoles, the Planck data do not suggest any upturn, contrary to the expectation based on the integrated Sachs-Wolfe contribution in the best-fit ΛCDM cosmology. |
Keywords | CMBR theory; integrated Sachs-Wolfe effect; physics of the early universe |
Download | arXiv • Journal |
Citing This Document | Amir Aghamousa, Arman Shafieloo, Mihir Arjunwadkar, and Tarun Souradeep , Unveiling acoustic physics of the CMB using nonparametric estimation of the temperature angular power spectrum for Planck . Technical Report CMS-TR-20141211 of the Centre for Modeling and Simulation, Savitribai Phule Pune University, Pune 411007, India (2014); available at http://cms.unipune.ac.in/reports/. |
Notes, Published Reference, Etc. | Published in the Journal of Cosmology and Astroparticle Physics as JCAP02(2015)007 |
Contact | amir AT apctp.org, arman AT apctp.org |
Supplementary Material |