PI: Anastasia Fialkov
Project Contributors: A. Fialkov (PI), J. Dhandha, T. Gessey-Jones, S. Pochinda, A. Tocher (University of Cambridge)
How Fuzzy Dark Matter Disrupts the Birth of the First Stars The Cold Dark Matter (CDM) paradigm struggles with small-scale galactic discrepancies. Fuzzy Dark Matter (FDM) composed of ultra-light axions offers a compelling alternative, utilizing macroscopic quantum wave properties to smooth dense halo cores. However, its impact on early-universe gas collapse and first star formation has remained largely unexplored. In this project in prep. we ran computationally demanding AREPO and AXIREPO simulations modelling the assembly of early halos to observe how FDM wave dynamics affect primordial gas accretion and cooling, as well s formation of sink particles which are a proxy for star formation. The simulations revealed that FDM fundamentally reshapes early star-forming regions. FDM features a central solitonic core that undergoes constant density fluctuations and a stochastic random walk. This time-varying gravitational potential actively “stirs” the gas, injecting turbulence and angular momentum that prevents efficient gas collapse. Furthermore, this dynamical stirring redistributes molecular hydrogen, the dominant coolant in primordial gas, from the dense core into the extended halo outskirts. FDM significantly delays and suppresses the accumulation of star-forming gas, forcing a transition from a singular central star forming region to fragmented, spatially diffuse clusters, as is show in the Figure.
Figure: Distribution of gas and sink particles in full FDM, frozen FDM and CDM (Tocher et al. in prep.)
Developing 21-cm cosmological simulations The first billion years of the universe represent a critical missing puzzle piece in our understanding of galaxy formation. The primary probe for this era is the 21-cm line of neutral hydrogen. To interpret data from current and future radio telescopes (such as SARAS, REACH, HERA, and the SKA) as well as observations of high-redshift galaxies by the James Webb Space Telescope (JWST), a realistic model of the universe and the predicted 21-cm signal are required. Our team designed and ran updated simulations of high-redshift Universe that include Population III and Population II stars to explore (1) the possibility of detecting Pop III and constraining their initial mass function (IMF) using the upcoming SKA (Gessey-Jones et al. 2025); (2) We jointly analyzed the simulated 21- cm signals with high-redshift UV luminosity functions from JWST and Hubble, and inferred the star-formation efficiency of the earliest dark matter halos (Dhandha et al. 2025); (3) to fully utilize the gigaparsec scales covered by upcoming instruments like SKA1-Low, we developed super-rezolution simulations using machine learning methods (Pochinda et al. 2025).