Addressing Synchrotron Challenges for CMB Observations: ELFS-SA Collaboration for Robust Foreground Removal

TL;DR

This paper discusses the ELFS-SA collaboration's plan to install low-frequency receivers on the Simons Array to improve foreground removal in CMB observations, enhancing the detection of primordial gravitational waves.

Contribution

It introduces a new low-frequency measurement approach that improves foreground modeling and robustness in future CMB experiments.

Findings

Enhanced knowledge of synchrotron spectral energy distribution.

Improved robustness of tensor-to-scalar ratio measurement.

Complementary low-frequency data benefits CMB foreground removal.

Abstract

Upcoming cosmic microwave background (CMB) experiments aim to detect primordial gravitational waves with unprecedented sensitivity. Effective foreground removal is essential to avoid biases in the measurement of the tensor-to-scalar ratio ($r$) in this high-precision regime. Recent analyses highlight the unexpected complexity of synchrotron emission at low frequencies, underscoring the need for more sensitive low-frequency data. To address this challenge, the European Low-Frequency Survey (ELFS) initiative and the Simons Array collaboration propose installing two European low-frequency receivers on one of the Simons Array telescopes. These receivers will enable measurements in the Southern Hemisphere between $6$ and $20$,GHz, complementary to those of current and proposed experiments targeting the measurement of cosmological gravitational waves. In this work, we study the benefits of combining these low-frequency observations with a representative future CMB experiment operating from the Southern Hemisphere. We find that the extra information can improve the knowledge of the underlying synchrotron spectral energy distribution (SED), with positive impacts on the robustness of measurement of the tensor-to-scalar ratio, $r$, against the complexity of low-frequency foregrounds.