Prospects for Probing Feedback from the First Black Holes and Stars During Reionization

TL;DR

This paper explores the potential of using high-redshift HI 21-cm observations to study feedback effects from the first stars and black holes during reionization, and proposes a technology roadmap for such measurements.

Contribution

It assesses the feasibility of detecting the HI signal from the early Universe and outlines a plan for future low-frequency radio observations, including lunar farside arrays.

Findings

Possible to map hydrogen distribution during reionization

Constraints on first star and black hole formation

Limits on exotic heating mechanisms before star formation

Abstract

The feasibility of making highly redshifted HI 21-cm (rest frame) measurements from an early epoch of the Universe between the Dark Ages and Reionization (i.e., z>6 and nu<200 MHz) to probe the effects of feedback from the first stars and quasars is assessed in this paper. It may be possible to determine the distribution of hydrogen through the Universe and to constrain the birth of the first stars and black holes via HI tomography. Such observations may also place limits on the properties of Inflation and any exotic heating mechanisms before the first star formation begins (e.g., dark matter decay). The global (all-sky) HI signal after Recombination has distinct features at different frequencies between 30 and 200 MHz that changes as the relative balance between the CMB and spin temperatures changes due to the expansion of the Universe and the ignition of stars and/or black holes. A technology roadmap to approach these observations beginning with ground-based arrays and ending with a low frequency radio array on the lunar farside is described.