Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008mnras.383.1195w&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 383, Issue 3, pp. 1195-1209.
Astronomy and Astrophysics
Astronomy
35
Galaxies: High-Redshift, Intergalactic Medium, Cosmology: Theory, Diffuse Radiation, Large-Scale Structure Of Universe
Scientific paper
Low-frequency observatories are currently being constructed with the goal of detecting redshifted 21-cm emission from the epoch of reionization. These observatories will also be able to detect intensity fluctuations in the cumulative 21-cm emission after reionization, from hydrogen in unresolved damped Lyα absorbers (such as gas-rich galaxies) down to a redshift z ~ 3.5. The inferred power spectrum of 21-cm fluctuations at all redshifts will show acoustic oscillations, whose comoving scale can be used as a standard ruler to infer the evolution of the equation of state for the dark energy. We find that the first generation of low-frequency experiments (such as MWA or LOFAR) will be able to constrain the acoustic scale to within a few per cent in a redshift window just prior to the end of the reionization era, provided that foregrounds can be removed over frequency bandpasses of >~8MHz. This sensitivity to the acoustic scale is comparable to the best current measurements from galaxy redshift surveys, but at much higher redshifts. Future extensions of the first-generation experiments (involving an order of magnitude increase in the antennae number of the MWA) could reach sensitivities below 1 per cent in several redshift windows and could be used to study the dark energy in the unexplored redshift regime of 3.5 <~ z <~ 12. Moreover, new experiments with antennae designed to operate at higher frequencies would allow precision measurements (<~1 per cent) of the acoustic peak to be made at more moderate redshifts (1.5 <~ z <~ 3.5), where they would be competitive with ambitious spectroscopic galaxy surveys covering more than 1000 deg2. Together with other data sets, observations of 21-cm fluctuations will allow full coverage of the acoustic scale from the present time out to z ~ 12.
Geil Paul M.
Loeb Abraham
Wyithe Stuart J. B.
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