Probing light relics through cosmic dawn
Nanoom Lee, Selim C. Hotinli

TL;DR
Upcoming 21-cm surveys of cosmic dawn, combined with CMB and large-scale structure data, can significantly improve constraints on light relic particles and other cosmological parameters, surpassing current sensitivities.
Contribution
This paper demonstrates that 21-cm observations during cosmic dawn can enhance constraints on $N_{eff}$ and other parameters beyond existing and upcoming CMB and galaxy surveys.
Findings
21-cm surveys can probe $N_{eff}$ at 2σ level with sensitivity of 0.034.
Combining 21-cm data with CMB improves parameter sensitivities by over a factor of 2.
21-cm data helps break degeneracies between $N_{eff}$ and helium fraction $Y_p$.
Abstract
We explore the prospects of upcoming 21-cm surveys of cosmic dawn () to provide cosmological information on top of upcoming cosmic microwave background (CMB) and large-scale structure surveys, such as CMB-S4, Simons Observatory (SO) and DESI. We focus on the effective number of relativistic species which is a promising observable for probing beyond the Standard Model theories. We show including upcoming 21-cm surveys such as the Square Kilometre Array (SKA) can allow probing a wide range of models for light particles at level achieving with CMB-S4, for example. Taking into account the degeneracy between and primordial helium fraction , one can achieve improvements in sensitivities to cosmological parameters, in particular, by more than a factor of 2 for and dark matter…
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Taxonomy
TopicsRadio Astronomy Observations and Technology · Astrophysics and Cosmic Phenomena · Computational Physics and Python Applications
