Miguel Morales — Page 2

arXiv2009

Cosmology from the Highly-Redshifted 21 cm Line

One of the next decade's most exciting prospects is to explore the cosmic "dark ages," during which the first stars in the Universe formed, with the 21 cm line of neutral hydrogen. At z>6, this light redshifts into the low-frequency radio regime and can be observed with new generations of wide-field arrays. These experiments have the potential to observe enormous volumes and to improve both cosmological and astrophysical constraints dramatically. In this white paper, we describe how the next decade will see the first steps toward unlocking this potential, allowing us to answer two key questions about the fundamental physics of our Universe and the intergalactic medium: Does the standard cosmological model describe the Universe during the "dark ages?" How did the intergalactic medium evolve during this important time, ending with the reionization of hydrogen?

astro-ph.CO↗

arXiv2009

Astrophysics from the Highly-Redshifted 21 cm Line

The cosmic dark ages and the epoch of reionization, during which the first generations of stars and galaxies formed, are among the most compelling frontiers of extragalactic astrophysics and cosmology. Here we describe an exciting new probe of these eras: the 21 cm line of neutral hydrogen, which will allow us to map the neutral intergalactic medium throughout the era of first galaxy formation. In this white paper, we describe how these studies can answer two key questions about galaxy formation: What were the properties of high-redshift galaxies? How did they affect the Universe around them?

astro-ph.CO↗

arXiv2007

Biased Reionisation and Non-Gaussianity in Redshifted 21cm Intensity Maps of the Reionisation Epoch

Spatial dependence in the statistics of redshifted 21cm fluctuations promises to provide the most powerful probe of the reionisation epoch. In this paper we consider the second and third moments of the redshifted 21cm intensity distribution using a simple model that accounts for galaxy bias during the reionisation process. We demonstrate that skewness in redshifted 21cm maps should be substantial throughout the reionisation epoch and on all angular scales, owing to the effects of galaxy bias which leads to early reionisation in over-dense regions of the IGM. The variance (or power-spectrum) of 21cm fluctuations will exhibit a minimum in redshift part way through the reionisation process, when the global ionisation fraction is around 50%. This minimum is generic, and is due to the transition from 21cm intensity being dominated by over-dense too under-dense regions as reionisation progresses. We show that the details of the reionisation history, including the presence of radiative feedback are encoded in the evolution of the auto-correlation and skewness functions with redshift and mean IGM neutral fraction. We discuss the detection of skewness by first generation instruments, and conclude that the Mileura Widefield Array - Low Frequency Demonstrator will have sufficient sensitivity to detect skewness on a range of angular scales at redshifts near the end of reionisation, while a subsequent instrument of 10 times the collecting area could map out the evolution of skewness in detail. The observation of a minimum in variance during the reionisation history, and the detection of skewness would both provide important confirmation of the cosmological origin of redshifted 21cm intensity fluctuations.

astro-ph↗