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J. D. Bowman (MIT), M. F. Morales (CfA), J. N. Hewitt (MIT)
The reionization history of the universe provides an important tool for understanding structure formation and the appearance of the first luminous objects. Existing experimental clues about the epoch of reionization (EOR) are confusing, however, and directly observing the process of structure formation would yield significant insights.
Neutral hydrogen emission from this period due to the redshifted 21 cm line should appear very faintly at low radio frequencies between 75 arrow 200 MHz (for redshifts 18 arrow 6). As the primordial hydrogen in the intergalactic medium cools and later reheats, density contrasts are revealed as fluctuations in the brightness temperature of the emission, and as the first luminous objects ionize their surroundings, bubbles appear.
Measuring the redshifted 21 cm fluctuation power spectrum and its evolution would provide a wealth of information about structure formation and the fundamental astrophysics of reionization. At high redshift, observations would explore structure formation in the linear gravity regime and constrain the properties of dark matter, and at lower redshifts, they would probe reionization and follow the emergence and properties of the first luminous objects.
The initial detection of redshited 21 cm emission from the EOR is anticipated to be a challenging experimental undertaking. The first generation of radio observatories targeting the full EOR power spectrum consists of three instruments that are currently under development: MWA, PAST, and LOFAR.
We present the results of calculations of the sensitivity of first generation EOR observatories using realistic design parameters such as antenna layout, field of view, and antenna temperature. We conclude that statistical observations of the EOR power spectrum should be obtainable below redshift 10 presuming foreground contamination can be mitigated. We also provide a fiducial mark for the capabilities of these observations to discern reionization scenarios and cosmological models.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.