Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd..12e..49c&link_type=abstract
Long Wavelength Astrophysics, 26th meeting of the IAU, Joint Discussion 12, 21 August 2006, Prague, Czech Republic, JD12, #49
Astronomy and Astrophysics
Astrophysics
Scientific paper
We will discuss the prospects for extracting cosmological and astrophysical parameters from the low radio frequency 21-cm background due to the spin-flip transition of neutral Hydrogen during and prior to the reionization of the Universe with radio interferometric arrays such as LOFAR and SKA We will discuss the measurement of the angular power spectrum of 21-cm anistropies, which exists due to inhomogeneities in the neutral Hydrogen density field, the gas temperature field, the intensity of the Lyman-alpha radiation from first luminous sources that emit UV photons, and the gas velocity. We consider the general case where fluctuations are induced by a variety of sources during the era of reionization. We attempt to extract parameters that describe both the underlying mass power spectrum and the global cosmology, as well as a set of simplified astrophysical parameters that connect fluctuations in the dark matter to those that govern 21-cm fluctuations by marginalizing over a model for the foregrounds at low radio frequencies. In this general description, we find large degeneracies between cosmological parameters and astrophysical parameters, though such degeneracies are not present when strong assumptions are made with respect to the spin temperature relative to the CMB temperature. Some of the parameter degeneracies are broken when 21-cm measurements are combined with information from the CMB, such as anisotropy and polarization measurements with Planck. For upcoming low frequency radio interferometers, the overall improvement on the cosmological parameter estimates when combined with Planck is not significant; we suggest that low radio frequency 21-cm measurements are, at best, suitable to understand certain astrophysical details during the era of recombination, but neither the shape of the power spectrum nor the global cosmological parameters.
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