Line of sight anisotropies in the Cosmic Dawn and EoR 21-cm power spectrum

TL;DR

This paper reviews how line of sight effects influence the 21-cm power spectrum during cosmic dawn and reionization, emphasizing their importance for future SKA-LOW observations and the Indian research community's contributions.

Contribution

It summarizes the Indian community's analytical and simulation efforts to understand line of sight effects in 21-cm cosmology for upcoming SKA-LOW surveys.

Findings

Line of sight effects significantly impact the 21-cm power spectrum.

Analytical models and simulations help quantify these effects.

Understanding these effects is crucial for accurate interpretation of future observations.

Abstract

The line of sight direction in the redshifted 21-cm signal coming from the cosmic dawn and the epoch of reionization is quite unique in many ways compared to any other cosmological signal. Different unique effects, such as the evolution history of the signal, non-linear peculiar velocities of the matter etc will imprint their signature along the line of sight axis of the observed signal. One of the major goals of the future SKA-LOW radio interferometer is to observe the cosmic dawn and the epoch of reionization through this 21-cm signal. It is thus important to understand how these various effects affect the signal for it's actual detection and proper interpretation. For more than one and half decades, various groups in India have been actively trying to understand and quantify the different line of sight effects that are present in this signal through analytical models and simulations. In many ways the importance of this sub-field under 21-cm cosmology have been identified, highlighted and pushed forward by the Indian community. In this article we briefly describe their contribution and implication of these effects in the context of the future surveys of the cosmic dawn and the epoch of reionization that will be conducted by the SKA-LOW.