The European Low Frequency Survey on the Simons Array

TL;DR

The European Low Frequency Survey (ELFS) aims to measure primordial B-mode polarization with high precision by observing Galactic and extragalactic emissions in the 5-120 GHz range, enhancing understanding of the early universe.

Contribution

This paper introduces the ELFS project, detailing its goals, instrumentation, and initial implementation with the Simons Array, focusing on foreground removal for CMB polarization studies.

Findings

Development of a 5.5-11 GHz receiver for ELFS-SA

Implementation of a digital backend with 1 MHz resolution

Initial deployment at the Atacama site

Abstract

In this paper we present the European Low Frequency Survey (ELFS), a project that will enable foregrounds-free measurements of the primordial $B$-mode polarization and a detection of the tensor-to-scalar ratio, $r$, to a level $\sigma(r) = 0.001$ by measuring the Galactic and extra-galactic emissions in the 5--120\,GHz frequency window. Indeed, the main difficulty in measuring the B-mode polarization comes from the fact that many other processes in the Universe also emit polarized microwaves, which obscure the faint Cosmic Microwave Background (CMB) signal. The first stage of this project is being carried out in synergy with the Simons Array (SA) collaboration, installing a 5.5--11\,GHz (X-band) coherent receiver at the focus of one of the three 3.5\,m SA telescopes in Atacama, Chile, followed by the installation of the QUIJOTE-MFI2 in the 10--20 GHz range. We designate this initial iteration of the ELFS program as ELFS-SA. The receivers are equipped with a fully digital back-end that will provide a frequency resolution of 1\,MHz across the band, allowing us to clean the scientific signal from unwanted radio frequency interference, particularly from low-Earth orbit satellite mega constellations. This paper reviews the scientific motivation for ELFS and its instrumental characteristics, and provides an update on the development of ELFS-SA.