The extraction of the desired signal from 21 cm cosmology experiments faces steep challenges: the combined issues of data size, weak signal, strong foregrounds, and complex instruments couple with sophisticated, constantly-evolving, multi-step software pipelines developed by large groups to produce a situation which undermines confidence in the final analysis. The challenges of producing...
I will present details of the first detection of cosmological signal using HI intensity mapping with a multi-dish array. For this we used the 64 dish MeerKAT telescope, a pathfinder for the Square Kilometre Array Observatory (SKAO), operating in single-dish mode, whereby the array is used as a collection of scanning auto-correlation dishes rather than as an interferometer. The detection is...
(SKA-Low) will map the distribution of neutral hydrogen during reionisation and produce a tremendous amount of 3D tomographic data. These image cubes will be subject to instrumental limitations, such as systematic noise, foreground contamination, radio frequency interference (RFI) and limited resolution. The challenge of this astronomy image is the undesired astronomical and instrumental noise...
The highly redshifted 21 cm emission line from neutral hydrogen has the potential to reveal the temperature, density, and ionization fraction of the IGM during the Cosmic Dawn, when the first stars and galaxies illuminated the universe. The Long Wavelength Array at the Owens Valley Radio Observatory (OVRO-LWA) is currently undergoing an upgrade that substantially improves its sensitivity to...
I will present ongoing work to better characterize the response of the Long Wavelength Array (LWA) antenna. Recent work has focused on directly measuring the impedance mismatch between the antenna and front end electronics (FEEs). Custom calibration and testing fixtures were created which allows for measurement of the antenna impedance at the feed points on the FEE boards. These measurements...
With unprecedented sensitivity and field of view, new generation radiotelescopes at low frequencies have to face new calibration challenges. One of the main drivers to cope with direction-dependent distortion (due to strong off-axis sources) is to develop a knowledge of beamshapes and how they vary in frequency and direction. I am going to present recent modelling work carried on VLA and...
