Post-reionization
The Inter-Galactic Medium (IGM) is highly ionized in the post-reionization era. The bulk of the HI at these redshifts is believed to reside in self-shielded gas clouds that appear as Damped Lyman-α systems (DLAs) in quasar spectra. These clouds are further believed to be associated with galaxies that are hosted in dark matter haloes. HI, therefore, is a tracer of galaxy distribution. The cumulative flux of the 21-cm radiation from these high redshift clouds appears as a diffused background radiation. Measurements of the intensity fluctuations in this diffused background provide us with a three-dimensional probe of the large scale structures over a large redshift range in the post-reionization era. The advantage of studying the 21-cm emission in the post-reionization era lies in the fact that the modulation of the signal due to complicated ionizing fields is less and the 21-cm power spectrum is directly proportional to the matter power spectrum which enhances its usefulness as a probe of cosmology.
The Inter-Galactic Medium (IGM) is highly ionized in the post-reionization era. The bulk of the HI at these redshifts is believed to reside in self-shielded gas clouds that appear as Damped Lyman-α systems (DLAs) in quasar spectra. These clouds are further believed to be associated with galaxies that are hosted in dark matter haloes. HI, therefore, is a tracer of galaxy distribution. The cumulative flux of the 21-cm radiation from these high redshift clouds appears as a diffused background radiation. Measurements of the intensity fluctuations in this diffused background provide us with a three-dimensional probe of the large scale structures over a large redshift range in the post-reionization era. The advantage of studying the 21-cm emission in the post-reionization era lies in the fact that the modulation of the signal due to complicated ionizing fields is less and the 21-cm power spectrum is directly proportional to the matter power spectrum which enhances its usefulness as a probe of cosmology.
This shows the simulated density contrasts of matter (left panels), halo (central panels), and neutral hydrogen HI (right panels) in the post-reionization era. [1605.02963]
This shows the simulated density contrasts of matter (left panels), halo (central panels), and neutral hydrogen HI (right panels) in the post-reionization era. [1605.02963]
This shows the neutral hydrogen bias at different k values. [1605.02963]
This shows the neutral hydrogen bias at different k values. [1605.02963]
This shows the effect of redshift space distortion in the 21-cm power spectrum. Here solid-red and dotted-blue contours respectively show power spectra in redshift and real space. [1801.07868]
This shows the effect of redshift space distortion in the 21-cm power spectrum. Here solid-red and dotted-blue contours respectively show power spectra in redshift and real space. [1801.07868]
This shows the HI bispectrum as function of cos-theta (angle between the two largest k-vectors). [1907.01819]
This shows the HI bispectrum as function of cos-theta (angle between the two largest k-vectors). [1907.01819]