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Foregrounds for 21-cmobservations ofneutral gas at highredshift S. Peng OhKatherine J. Mack2003 год

Foregrounds for 21-cm observations of neutral gas at high redshift
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Аннотация: We investigate a number of potential foregrounds for an ambitious goal of future radio telescopes such as the Square Kilometer Array (SKA) and the Low Frequency Array (LOFAR): spatial tomography of neutral gas at high redshift in 21-cm emission. While the expected temperature fluctuations due to unresolved radio point sources is highly uncertain, we point out that free–free emission from the ionizing haloes that reionized the Universe should define a minimal bound. This emission is likely to swamp the expected brightness temperature fluctuations, making proposed detections of the angular patchwork of 21-cm emission across the sky unlikely to be viable. Hα observations with JWST could place an upper bound on the contribution of high-redshift sources to the free–free background. An alternative approach is to discern the topology of reionization from spectral features due to 21-cm emission along a pencil-beam slice. This requires tight control of the frequency-dependence of the beam in order to prevent foreground sources from contributing excessive variance. We also investigate potential contamination by galactic and extragalactic radio recombination lines (RRLs). These are unlikely to be show-stoppers, although little is known about the distribution of RRLs away from the Galactic plane. The mini-halo emission signal is always less than that of the intergalactic medium (IGM), making mini-haloes unlikely to be detectable. If they are seen, it will be only in the very earliest stages of structure formation at high redshift, when the spin temperature of the IGM has not yet decoupled from the cosmic microwave background.
Год издания: 2003
Авторы: S. Peng Oh, Katherine J. Mack
Издательство: Oxford University Press
Источник: Monthly Notices of the Royal Astronomical Society
Ключевые слова: Radio Astronomy Observations and Technology, Astrophysics and Cosmic Phenomena, Galaxies: Formation, Evolution, Phenomena
Другие ссылки: Monthly Notices of the Royal Astronomical Society (PDF)
Monthly Notices of the Royal Astronomical Society (HTML)
CaltechAUTHORS (California Institute of Technology) (PDF)
CaltechAUTHORS (California Institute of Technology) (HTML)
DataCite API (HTML)