Probing the cosmic web with SKA

© Robin Kooistra

The large-scale filaments of the cosmic web can clearly be seen in the distribution of galaxies in large galaxy redshift surveys. However, the gas inside these filaments, the intergalactic medium (IGM), is much harder to detect due to its relatively low density. The upcoming Square Kilometre Array (SKA) will allow us to reach the required sensitivity for a detection of the 21cm emission from the neutral gas in the IGM.

In this work the positions of filaments are inferred from the distributions of galaxies. Using the hydrodynamical EAGLE simulation, a realistic estimate for the average filament signal was obtained, as shown in the top figure. The blue lines denote the filaments traced through the distribution of the galaxies. The level of the signal lies within reach of the first phase of the SKA by integrating all emission of a single filament. This will allow for statistical studies of the properties of the IGM by targeting filaments inferred from large galaxy surveys, such as SDSS.

The bottom figure shows an image of a filament from the simulation convolved with the beam of SKA as a function of redshift. The further away the filament, the less the diffuse IGM emission suffers from spatial filtering. The future upgrade to SKA-2 will make it possible to fully map the emission from filaments, making this a promising science case for this telescope.

The full details of this work can be found in Kooistra et al. 2019 (https://arxiv.org/abs/1909.09648)