21 cm observation of LSS at z~1 Instrument sensitivity and foreground subtraction

TL;DR

This paper evaluates the sensitivity of radio interferometers for 21cm intensity mapping to study large-scale structures at z~1, focusing on instrument configurations, foreground removal, and implications for Dark Energy constraints.

Contribution

It introduces a method to assess instrument sensitivity and foreground subtraction for 21cm LSS observations, demonstrating the potential of multi-beam radio arrays for cosmological studies.

Findings

Radio instruments with hundreds of beams can detect BAO at z~1.

Foreground removal effectively isolates the 21cm signal.

Optimized setups can constrain Dark Energy parameters.

Abstract

Large Scale Structures (LSS) in the universe can be traced using the neutral atomic hydrogen HI through its 21cm emission. Such a 3D matter distribution map can be used to test the Cosmological model and to constrain the Dark Energy properties or its equation of state. A novel approach, called intensity mapping can be used to map the HI distribution, using radio interferometers with large instantaneous field of view and waveband. In this paper, we study the sensitivity of different radio interferometer configurations, or multi-beam instruments for the observation of large scale structures and BAO oscillations in 21cm and we discuss the problem of foreground removal. For each configuration, we determine instrument response by computing the (u,v) or Fourier angular frequency plane coverage using visibilities. The (u,v) plane response is the noise power spectrum, hence the instrument sensitivity for LSS P(k) measurement. We describe also a simple foreground subtraction method to separate LSS 21 cm signal from the foreground due to the galactic synchrotron and radio sources emission. We have computed the noise power spectrum for different instrument configuration as well as the extracted LSS power spectrum, after separation of 21cm-LSS signal from the foregrounds. We have also obtained the uncertainties on the Dark Energy parameters for an optimized 21 cm BAO survey. We show that a radio instrument with few hundred simultaneous beams and a collecting area of ~10000 m^2 will be able to detect BAO signal at redshift z ~ 1 and will be competitive with optical surveys.