Probing the First Stars and Black Holes in the Early Universe with the Dark Ages Radio Explorer (DARE)

TL;DR

The DARE mission aims to detect the earliest cosmic signals from the first stars and black holes by measuring the redshifted 21-cm hydrogen line from the Dark Ages and Cosmic Dawn, using a lunar orbit to avoid interference.

Contribution

This paper proposes a novel space-based mission, DARE, to measure the sky-averaged 21-cm signal from the early universe, providing new insights into the formation of the first luminous objects.

Findings

Design of a lunar-orbiting radio instrument for 21-cm detection

Method for foreground removal using spectral calibration and MCMC

Expected to detect signals from 80-420 million years after the Big Bang

Abstract

A concept for a new space-based cosmology mission called the Dark Ages Radio Explore (DARE) is presented in this paper. DARE's science objectives include (1) When did the first stars form? (2) When did the first accreting black holes form? (3) When did Reionization begin? (4) What surprises does the end of the Dark Ages hold (e.g., Dark Matter decay)? DARE will use the highly-redshifted hyperfine 21-cm transition from neutral hydrogen to track the formation of the first luminous objects by their impact on the intergalactic medium during the end of the Dark Ages and during Cosmic Dawn (redshifts z=11-35). It will measure the sky-averaged spin temperature of neutral hydrogen at the unexplored epoch 80-420 million years after the Big Bang, providing the first evidence of the earliest stars and galaxies to illuminate the cosmos and testing our models of galaxy formation. DARE's approach is to measure the expected spectral features in the sky-averaged, redshifted 21-cm signal over a radio bandpass of 40-120 MHz. DARE orbits the Moon for a mission lifetime of 3 years and takes data above the lunar farside, the only location in the inner solar system proven to be free of human-generated radio frequency interference and any significant ionosphere. The science instrument is composed of a three-element radiometer, including electrically-short, tapered, bi-conical dipole antennas, a receiver, and a digital spectrometer. The smooth frequency response of the antennas and the differential spectral calibration approach using a Markov Chain Monte Carlo technique will be applied to detect the weak cosmic 21-cm signal in the presence of the intense solar system and Galactic foreground emissions.