Epoch of Reionization

The Cosmic Dawn/Epoch of Reionization Science Working Group organised a meeting which took place at the building of the Royal Astronomical Society in London, 24 – 25 September 2018. There were around 35 participants and most SKA countries were represented. During the meeting we received updates from the MWA, LOFAR and HERA EoR projects as well as from the SKA. We further had a series of shorter presentations mostly by younger scientists.

A large fraction of the meeting was dedicated to defining two “challenges”, the Data Challenge and the Theory Challenge. The Data Challenge will develop over time and will allow different teams to compare their performance on extracting the CD/EoR signal from simulated SKA data. The intention is to make the simulated SKA data more and more realistic over time, for example by including calibration errors and ionospheric effects. At the meeting the first Data Challenge was defined which consists ofthree data sets: 1) EoR signal with noise, 2) EoR signal with diffuse galactic foregrounds, 3) EoR signal with noise anddiffuse galactic foregrounds.

The data is provided both as uv data and as image cubes. The task is to extract the power spectra of the different signals (EoR, noise, foregrounds) from these datasets. Ten different groups have indicated that they will participate in this first Data Challenge. Modellers discussed the design of a Theory Challenge. The goal here is to ultimately produce reliable astrophysical parameter estimates from a simulated SKA 21-cm data set. However, before this can be achieved the different models first need to agree on a common approach to defining the parameters. It was agreed that this common approach would rely on different luminosity functions, e.g. the ionizing luminosity function, rather than parameters which describe how much radiation an individual dark matter halo/galaxy produces.

The local organisers, Jonathan Pritchard, Emma Chapman and Catherine Watkinson did a great job and the opportunity to see the building of the RAS, including a fragment of Newton’s apple tree, was enjoyed by all.

Report provided by the EoR SWG