Inflationary vs. Reionization Features from Planck 2015 Data

TL;DR

This paper investigates how features from inflation and reionization affect the Planck 2015 data, finding that certain anomalies can be explained by sharp suppression and high redshift ionization, with implications for future measurements.

Contribution

It provides a joint, model-independent analysis of inflationary and reionization features in CMB data, clarifying their interplay and impact on observed anomalies.

Findings

Preference for large-scale suppression driven by temperature spectrum feature

High redshift ionization favored by polarization excess at low multipoles

Inflationary and reionization features can be disentangled and tested with future data

Abstract

Features during inflation and reionization leave corresponding features in the temperature and polarization power spectra that could potentially explain anomalies in the Planck 2015 data but require a joint analysis to disentangle. We study the interplay between these two effects using a model-independent parametrization of the inflationary power spectrum and the ionization history. Preference for a sharp suppression of large scale power is driven by a feature in the temperature power spectrum at multipoles $\ell \sim 20$, whereas preference for a component of high redshift ionization is driven by a sharp excess of polarization power at $\ell \sim 10$ when compared with the lowest multipoles. Marginalizing inflationary freedom does not weaken the preference for $z \gtrsim 10$ ionization, whereas marginalizing reionization freedom slightly enhances the preference for an inflationary feature but can also mask its direct signature in polarization. The inflation and reionization interpretation of these features makes predictions for the polarization spectrum which can be tested in future precision measurements especially at $10\lesssim \ell \lesssim 40$.