New Insights into Ultralight Axion Dark Matter and Galaxy Formation

Recent research conducted by Harrison Winch, Keir K. Rogers, Renée Hložek, and David J. E. Marsh focuses on ultralight axion dark matter (DM) and its implications for galaxy formation. The study, titled "High-redshift, small-scale tests of ultralight axion dark matter using Hubble and Webb galaxy UV luminosities," utilizes data from the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST) to analyze the abundance of ultraviolet-bright galaxies in the presence of ultralight axion DM.

The researchers set limits on axion DM using both Planck cosmic microwave background (CMB) and ultraviolet luminosity function (UVLF) data. They found that axions suppress galaxy formation with a complex relationship depending on redshift and luminosity. Specifically, they excluded a single axion as all the DM for masses less than $10^{-21.6}$ eV and constrained axions with masses between $10^{-26}$ and $10^{-23}$ eV to be less than 22% of the DM at a 95% credibility level.

The study also highlights that the high-redshift measurements provide a consistency check for low-redshift tests of axion DM, particularly in relation to recent findings suggesting a sub-dominant ultralight axion DM fraction in Lyman-alpha forest data. The combination of HST and JWST data did not enhance constraints beyond those provided by HST alone, but future JWST measurements could significantly improve these results.

Additionally, the researchers noted an excess of low-mass halos at redshift less than 3, which may be further explored through sub-galactic structure probes such as stellar streams and satellite galaxies. This research bridges a gap in the understanding of axion mass and DM fraction that has not been previously constrained by cosmological data, potentially impacting future studies in cosmology and astrophysics.

For further details, the paper can be accessed via arXiv: arXiv:2404.11071.