How accurately can 21 cm tomography constrain cosmology?
- Center for Theoretical Physics, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)
There is growing interest in using 3-dimensional neutral hydrogen mapping with the redshifted 21 cm line as a cosmological probe. However, its utility depends on many assumptions. To aid experimental planning and design, we quantify how the precision with which cosmological parameters can be measured depends on a broad range of assumptions, focusing on the 21 cm signal from 6<z<20. We cover assumptions related to modeling of the ionization power spectrum, to the experimental specifications like array layout and detector noise, to uncertainties in the reionization history, and to the level of contamination from astrophysical foregrounds. We derive simple analytic estimates for how various assumptions affect an experiment's sensitivity, and we find that the modeling of reionization is the most important, followed by the array layout. We present an accurate yet robust method for measuring cosmological parameters that exploits the fact that the ionization power spectra are rather smooth functions that can be accurately fit by 7 phenomenological parameters. We find that for future experiments, marginalizing over these nuisance parameters may provide constraints almost as tight on the cosmology as if 21 cm tomography measured the matter power spectrum directly. A future square kilometer array optimized for 21 cm tomography could improve the sensitivity to spatial curvature and neutrino masses by up to 2 orders of magnitude, to {delta}{omega}{sub k}{approx_equal}0.0002 and {delta}m{sub {nu}}{approx_equal}0.007 eV, and give a 4{sigma} detection of the spectral index running predicted by the simplest inflation models.
- OSTI ID:
- 21250349
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 78, Issue 2; Other Information: DOI: 10.1103/PhysRevD.78.023529; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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