The All-Sky SignAl Short-Spacing INterferometer (ASSASSIN) I: Global sky measurements with the Engineering Development Array-2

Abstract

Aiming to fill a crucial gap in our observational knowledge of the early Universe, experiments around the world continue to attempt to verify the claimed detection of the redshifted 21-cm signal from Cosmic Dawn by the EDGES experiment. This sky-averaged or 'global' signal from neutral hydrogen should be detectable at low radio frequencies (50-200 MHz), but is difficult to measure due to bright foreground emission and difficulties in reaching the required levels of instrumental-calibration precision. In this paper we outline our progress toward using a novel new method to measure the global redshifted 21-cm signal. Motivated by the need to use alternative methods with very different systematic errors to EDGES for an independent result, we employ an array of closely-spaced antennas to measure the global sky signal interferometrically, rather than using the conventional approach with a single antenna. We use simulations to demonstrate our newly-developed methods and show that, for an idealised instrument, a 21-cm signal could theoretically be extracted from the visibilities of an array of closely-spaced dipoles. We verify that our signal-extraction methods work on real data using observations made with a Square Kilometre-Array-like prototype; the Engineering Development Array-2. Finally, we use the lessons learned in both our simulations and observations to lay out a clear plan for future work, which will ultimately lead to a new global redshifted 21-cm instrument: the All-Sky SignAl Short-Spacing INterferometer (ASSASSIN).

18 pages, 13 figures

References in corpus (10)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• Post-correlation radio frequency interference classification methods
• Foreground Model and Antenna Calibration Errors in the Measurement of the Sky-Averaged λ21 cm Signal at z~20
• Improved Measurement of the Spectral Index of the Diffuse Radio Background Between 90 and 190 MHz
• GMOSS: All-sky model of spectral radio brightness based on physical components and associated radiative processes
• Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz
• Modelling and peeling extended sources with shapelets: a Fornax A case study
• The Engineering Development Array: A low frequency radio telescope utilising SKA precursor technology
• Design Equations for a Closely-Spaced Two-Element Interferometer Including Internal Noise Coupling

Cited by in corpus (12)

• SARAS 3 CD/EoR Radiometer: Design and Performance of the Receiver
• Mapper of the IGM spin temperature: instrument overview
• A Bayesian Calibration Framework for EDGES
• Probing the primordial Universe with 21-cm line from cosmic dawn/epoch of reionization
• Sensitivity of the Global 21-cm Signal to Dark Matter-Baryon Scattering
• Improvements to the Search for Cosmic Dawn Using the Long Wavelength Array
• Optimization of Antenna Performance for Global 21-cm Observations and Verification Using Scaled Copies
• On Measuring the 21 cm Global Spectrum of the Cosmic Dawn with an Interferometer Array
• The impact of lunar topography on the 21-cm power spectrum for grid-based arrays : Insights for the Dark-ages EXplorer (DEX)
• Beamforming approaches toward detecting the 21-cm global signal from Cosmic Dawn with radio array telescopes
• Nonlinear reconstruction of 21cm global signal from 21cm power spectrum with artificial neural networks
• Imaging the Southern Sky at 159MHz using Spherical Harmonics with the Engineering Development Array 2