The 21cm line emission from neutral hydrogen is a key quantity to understand the Epoch of Reionization, where the first stars and galaxies were formed and ionized the intergalactic hydrogen. However, due to the weakness of the signal and the presence of huge foreground, the 21cm line signal has never been detected so far. In this project, we aim to detect the 21cm line signal from the Epoch of Reionization for the first time, using a low-frequency radio interferemeter, Muchison Widefield Array (MWA), located in Australia.
In the 100 MHz band, in addition to this signal, there are foreground radiation such as galactic and extragalactic radio objects, and their intensity is much stronger than the signal. Therefore, precise removal of these foreground emissions is critical to signal detection. Therefore, we will develop methods to estimate and remove the spectrum and spatial distribution of foreground radiation using advanced statistical methods such as sparse modeling. Further, avoidance of foreground with cross-correlation between 21cm line signal and galaxies will be pursued using machine learning methods such as artificial neural network.
The MWA is a radio interferometers and the distribution of radio intensity in the sky can be obtained by combining the signal phase differences of all pairs of antennas. However, because the number of antennas is finite, the intensity distribution can not be completely reconstructed. This is a serious problem in observing the size and shape of the ionizing bubbles formed around the first stars. We use sparse modeling techniques to interpolate such missing data and obtain accurate intensity maps.
Unit leaderKeitaro TAKAHASHIAssociate Professor, Faculty of Advanced Science and Technology, Kumamoto UniversityJapan
Rachel WEBSTERProfessor, The University of MelbourneAustralia
Bart PINDORAcademic, The University of MelbourneAustralia
Shintaro YOSHIURAJSPS Researcher, The University of MelbourneAustralia
Takuya AKAHORIResearcher, National Astronomical Observatory of JapanJapan
Takeshi FUKUSAKOProfessor, Kumamoto UniversityJapan