Dark matter and the first galaxies

Abstract

This new initiative will model the impact of dark matter properties on the era when the first stars and galaxies formed. Compelling evidence indicates that dark matter makes up about 85% of the mass in the universe, but its properties remain completely mysterious. Despite decades of effort, searches for previously favored cold dark matter candidates have come up empty, motivating the study of alternatives. Possibilities include fuzzy dark matter, warm dark matter and extreme ultra-light axion dark matter. These possibilities preserve the well tested, large-scale features of cold dark matter, yet make distinctive predictions on smaller scales. Specifically, in some models the number of small mass dark matter clumps and the level of internal structure within clumps is suppressed relative to the case of cold dark matter, while in other models these may be enhanced. The suppression or enhancement of small-scale structures will, in turn, lead to a distinctive delay or a head-start for when the first stars and galaxies formed. Revolutionary new data will soon probe this time period for the first time and enable novel tests of dark matter’s properties. First, the James Webb Space Telescope is now fully operational and already producing ground-breaking science images. Its infrared data will ultimately transform our understanding of the first galaxies. Second, ground-based surveys are underway to make pioneering, unprecedented detections of t21 cm radio-wave signals from intergalactic neutral hydrogen during the era of the first stars and galaxies. The interdisciplinary research team--combining complementary expertise in dark matter physics, the astrophysics of galaxy formation and the intergalactic medium--will develop a comprehensive modeling framework to best identify dark matter’s observational signatures in the upcoming data using four distinct and powerful empirical tests.

 

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