Studying the multifrequency angular power spectrum of the cosmic dawn 21-cm signal

The light-cone (LC) anisotropy arises due to cosmic evolution of the cosmic dawn (CD) 21-cm signal along the line-of-sight (LoS) axis of the observation volume. The LC effect makes the signal statistically non-ergodic along the LoS axis. The multifrequency angular power spectrum (MAPS) provides an unbiased alternative to the popular three-dimensional (3D) power spectrum as it does not assume statistical ergodicity along every direction in the signal volume. Unlike the 3D power spectrum which mixes the cosmic evolution of the 21-cm signal along the LoS k modes, MAPS keeps the evolution information disentangled. Here, we first study the impact of different underlying physical processes during CD on the behaviour of the 21-cm MAPS using simulations of various different scenarios and models. We also make error predictions in 21-cm MAPS measurements considering only the system noise and cosmic variance for mock observations of Hydrogen Epoch of Reionization Array (HERA), NenuFAR, and SKA-Low. We find that 100 h of HERA observations will be able to measure 21-cm MAPS at >= 3 sigma for <= 1000 with 0. 1 MHz channel-width. The better sensitivity of SKA-Low allows reaching this sensitivity up to <= 3000. Note that due to the difference in the frequency coverage of the various experiments, the CD-epoch of reionization model considered for NenuFAR is different than those used for the HERA and SKA-Low predictions. Considering NenuFAR with the new model, measurements >= 2 sigma are possible only for <= 600 with 0. 2 MHz channel-width and for a 10 times longer observation time of t (obs) = 1000 h. However, for the range 300 <= <= 600 and t obs = 1000 h more than 3smeasurements are still possible for NenuFAR when combining consecutive frequency channels within a 5 MHz band.

Automated summary

The LC anisotropy of the cosmic dawn 21-cm signal along the LoS axis leads to non-ergodicity, which can be resolved using the MAPS. Unlike the 3D power spectrum, MAPS separates the cosmic evolution information of the signal along the LoS k modes. Simulation studies show that HERA and SKA-Low can measure the 21-cm MAPS at high significance levels, while NenuFAR requires a longer observation time and narrower channel width for significant measurements.