Neutral hydrogen at high redshifts as a probe of structure formation - II: line profiles of a protocluster

Kumar, A. ; Padmanabhan, T. ; Subramanian, K. (1995) Neutral hydrogen at high redshifts as a probe of structure formation - II: line profiles of a protocluster Monthly Notices of the Royal Astronomical Society, 272 (3). pp. 544-550. ISSN 0035-8711

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The formation of structures at z≲10.0 can be proved using the 21-cm line emission from the neutral hydrogen. Two of us (KS and TP, Paper I) previously computed the expected abundance of protoclusters as a function of the flux density at various redshifts, in the cold dark matter (CDM) and the hot dark matter (HDM) models. As a complement to Paper I, here we work out in detail how the HI line profile from a spherically symmetric protocluster evolves as it decouples from Hubble expansion and collapses. Our paradigm for structure formation is the CDM model where structures form hierarchically. Neutral hydrogen, in the small-scale clumps that form the protocluster, is the source of HI line emission. We find that the peak fluxes of the HI line profile in this model are typically of order 0.5-0.7 mJy, while the widths (FWHM) are of order 0.3-1.8 MHz. The major uncertainty in our calculations is the fraction of mass of the protocluster in the form of neutral hydrogen. If the neutral hydrogen factor ƒ is of the order of the value we have adopted (ƒ=0.025) in our calculations or greater, then a typical protocluster could indeed be detectable by future facilities, like the Giant Metrewave Radio Telescope (GMRT) which is currently being built in India. If the neutral hydrogen fraction is much less than the value we have adopted, then a more sensitive instrument is needed to detect the HI line emission from a typical protocluster.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons.
Keywords:Galaxies: Formation; Dark Matter; Large-scale Structure of Universe; Radio Line: General
ID Code:72485
Deposited On:29 Nov 2011 05:31
Last Modified:29 Nov 2011 05:31

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