ARTS4SKA (Accelerated Radiative Transfer Simulations for the Square Kilometre Array)
The Epoch of Reionisation (EoR)
Approximately 380,000 years after the Big Bang, the temperature of the Universe dropped sufficiently for neutral hydrogen and helium to form, initiating the cosmological dark ages. Over time, gravitational instability led to the emergence of the first luminous sources, primordial stars, galaxies, and accreting black holes. Their radiation transformed the intergalactic medium (IGM) from a cold, neutral state into a warm, ionised plasma. This transition, known as the Epoch of Reionisation (EoR), marks a fundamental phase in cosmic history and the beginning of the era of galaxies.
Observing Reionisation with the Square Kilometre Array (SKA)
The external page Square Kilometre Array Observatory (SKAO) project is an international effort to build the world’s largest radio telescope to probe this early period of structure formation. The low-frequency component of this telescope, SKA-Low, will provide direct observational access to the EoR, enabling us to revolutionise our understanding of the Universe and answer the pressing questions: What are the primary sources of reionisation? When does reionisation begin and end? What is the topology of the ionised region? What can be learned about early galaxies from the reionisation and vice versa? How does reionisation later affect galaxy formation?
The study of the EoR requires careful physical treatment, which can only be achieved with Radiative Transfer (RT) simulations. EoR is inherently a multi-scale problem, requiring codes that simulate large-scale dynamics while resolving physical processes that occur on galactic scales. Several authors have tackled this problem, nevertheless, current RT codes struggle to concurrently account for the large volumes and the physical processes occurring at small scales detectable by SKA-Low observations.
ARTS4SKA: A New Generation of Radiative Transfer Simulations
With the Accelerated Radiative Transfer Simulation for Square Kilometre Array (ARTS4SKA) project, we propose to develop the first code that not only simulates the large-scale required for future SKA-Low observations but also includes a complete treatment of all relevant physical processes on the galactic scale. In this project, we are improving the existing Accelerated Short-characteristics Octahedral RAytracing (ASORA) method, a portable raytracing algorithm, written in C++/CUDA and wrapped in a Python interface, specifically designed to run on GPUs without compromising computational efficiency.
In January 2022, Switzerland joined the SKAO, alongside nine national institutions that formed the SKA Swiss Consortium (SKACH), with the goal of managing Switzerland’s scientific and technological contributions to the SKAO. The proposed project will leverage SKACH's unique expertise in cosmology, astrophysics, and computer science (Machine Learning and HPC), and is carried out by an interdisciplinary team from ETHZ, ZHAW, the University of Basel, and EPFL.
