H i as a probe of the large-scale structure in the post-reionization universe

• Published in: Monthly notices of the Royal Astronomical Society Vol. 407; no. 1; pp. 567 - 580
• Main Authors: Bagla, J. S., Khandai, Nishikanta, Datta, Kanan K.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.09.2010; Wiley-Blackwell; Oxford University Press
• Subjects: Arrays; Astronomi; Astronomi och astrofysik; Astronomy; Astronomy and astrophysics; Astrophysics; Computer simulation; Correlation; Earth, ocean, space; Exact sciences and technology; Fysik; galaxies: evolution; galaxies: ISM; Hydrogen; large-scale structure of Universe; Mathematical analysis; Mathematical models; methods: numerical; NATURAL SCIENCES; NATURVETENSKAP; Physics; radio lines: galaxies; Radio telescopes; Small scale; Star & galaxy formation; Stars & galaxies; Universe; Visibility; radio lines: galaxies; methods: numerical; galaxies: evolution; galaxies: ISM; large-scale structure of Universe; Galaxy evolution; Red shift; Fluctuations; Galaxies; Radio galaxies; Power spectra; Digital simulation; N body system; Probability distribution; Numerical method; Large-scale structure; Neutral hydrogen; Theoretical model; Dark matter; Correlations; Cosmic radio sources; Visibility; Gravity
• ISSN: 0035-8711; 1365-2966; 1365-2966
• DOI: 10.1111/j.1365-2966.2010.16933.x

We model the distribution of neutral hydrogen (H i) in the post-reionization universe. This model uses gravity-only N-body simulations and an ansatz to assign H i to dark matter haloes that is consistent with observational constraints and theoretical models. We resolve the smallest haloes that are likely to host H i in the simulations; care is also taken to ensure that any errors due to the finite size of the simulation box are small. We then compute the smoothed one-point probability distribution function and the power spectrum of fluctuations in H i. This is compared with other predictions that have been made using different techniques. We highlight the significantly high bias for the H i distribution at small scales. This aspect has not been discussed before. We then discuss the prospects of the detection with the Murchison Widefield Array (MWA), Giant Meterwave Radio Telescope (GMRT) and the hypothetical MWA5000. The MWA5000 can detect visibility correlations at large angular scales at all redshifts in the post-reionization era. The GMRT can detect visibility correlations at lower redshifts; specifically there is a strong case for a survey at z≃ 1.3. We also discuss prospects for direct detection of rare peaks in the H i distribution using the GMRT. We show that direct detection should be possible with an integration time that is comparable to, or even less than, the time required for a statistical detection. Specifically, it is possible to make a statistical detection of the H i distribution by measuring the visibility correlation and direct detection of rare peaks in the H i distribution at z≃ 1.3 with the GMRT in less than 1000 h of observations.