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The Global 21 Centimeter Background from High Redshifts

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arxiv astro-ph/0604040 v1 pith:MCVJWGCW submitted 2006-04-03 astro-ph

classification astro-ph
keywords backgroundreionizationstarsamplitudebeforedominateduringepoch
verification ladder T0 review T1 audit T2 compute T3 formal
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We consider the evolution of the sky-averaged 21 cm background during the early phases of structure formation. Using simple analytic models, we calculate the thermal and ionization histories, assuming that stellar photons dominate the radiation background. The resulting 21 cm spectra can constrain the properties of the first generations of stars and quasars. If Population II stars dominate, Lyman-alpha coupling renders the IGM visible before it is heated by X-rays and long before reionization. Thus the 21 cm background has a strong absorption epoch followed by weaker emission that fades during reionization. The harder spectra of very massive Population III stars compress these transitions into a shorter time interval and decreases the signal amplitude. However, the reionization epoch will remain visible except in extreme cases. The global 21 cm signal will be challenging to observe because of astronomical foregrounds, but it offers an exciting opportunity to study the first sources of light. It also fixes the overall amplitude of the fluctuating background whose detection is a major goal of several next-generation low-frequency radio interferometers.

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Cited by 5 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. The Rise and Fall of Acoustic Oscillations at Cosmic Dawn

    astro-ph.CO 2026-07 conditional novelty 7.0 of 10

    Ignoring the percent-level phase offset between BAO and VAO features in the cosmic-dawn 21-cm power spectrum biases H(z) by ~2%; joint BAO–VAO templates are required for standard-ruler inference.

  2. Global 21cm Measurement Calibration Methodology

    astro-ph.CO 2026-07 accept novelty 5.0 of 10

    Three-way Dicke switching is inadequate for broadband global 21cm work; five independent calibrators plus the classical four noise parameters yield the correct absolute temperature, and Rogers & Bowman (2012) missed |...

  3. A hidden reionization prior biases cosmological inference

    astro-ph.CO 2026-06 unverdicted novelty 5.0 of 10

    No monotonic reionization history fits Planck τ, patchy kSZ from SPT/ACT, and Lyα endpoint; an early ionization phase at z≳12 relaxes ∑mν<0.39 eV and shifts σ8 via As-τ degeneracy.

  4. Imprints of energy injection by compact dark stars in the 21-cm signal

    hep-ph 2025-04 unverdicted novelty 5.0 of 10

    Compact dark stars from asymmetric dark matter may inject energy that significantly deviates the 21-cm brightness temperature evolution from standard cosmology, offering a new probe for particle dark matter.

  5. Analytical modeling of the one-dimensional power spectrum of 21-cm forest based on a halo model method

    astro-ph.CO 2024-11 conditional novelty 5.0 of 10

    A halo-model formula for the 1D power spectrum of the 21-cm forest is presented and shown to match small-scale simulations built from the same gas and temperature assumptions.

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