Maximum likelihood, parametric component separation and CMB B-mode detection in suborbital experiments

TL;DR

This study evaluates the effectiveness of the parametric Maximum Likelihood method in separating CMB B-mode signals from foregrounds in suborbital experiments, demonstrating potential for detecting low tensor-to-scalar ratios with controlled systematics.

Contribution

It provides a detailed analysis of foreground residuals and detection limits for next-generation balloon-borne and ground-based CMB experiments using parametric maximum likelihood separation.

Findings

Residual foregrounds are low for balloon experiments, minimally affecting B-mode detection.

Ground-based experiments require external information for effective foreground cleaning.

Both experiment types can detect r as low as ~0.04 if systematics are well-controlled.

Abstract

We investigate the performance of the parametric Maximum Likelihood component separation method in the context of the CMB B-mode signal detection and its characterization by small-scale CMB suborbital experiments. We consider high-resolution (FWHM=8') balloon-borne and ground-based observatories mapping low dust-contrast sky areas of 400 and 1000 square degrees, in three frequency channels, 150, 250, 410 GHz, and 90, 150, 220 GHz, with sensitivity of order 1 to 10 micro-K per beam-size pixel. These are chosen to be representative of some of the proposed, next-generation, bolometric experiments. We study the residual foreground contributions left in the recovered CMB maps in the pixel and harmonic domain and discuss their impact on a determination of the tensor-to-scalar ratio, r. In particular, we find that the residuals derived from the simulated data of the considered balloon-borne observatories are sufficiently low not to be relevant for the B-mode science. However, the ground-based observatories are in need of some external information to permit satisfactory cleaning. We find that if such information is indeed available in the latter case, both the ground-based and balloon-borne experiments can detect the values of r as low as ~0.04 at 95% confidence level. The contribution of the foreground residuals to these limits is found to be then subdominant and these are driven by the statistical uncertainty due to CMB, including E-to-B leakage, and noise. We emphasize that reaching such levels will require a sufficient control of the level of systematic effects present in the data.