Detecting the Earliest Galaxies through Two New Sources of 21 Centimeter Fluctuations

By R. Barkana, Abraham Loeb. 2004

213 citations recorded by the source corpus.

The first galaxies that formed at a redshift z ~ 20-30 emitted continuum photons with energies between the Lyα and Lyman limit wavelengths of hydrogen, to which the neutral universe was transparent except at the Lyman series resonances. As these photons redshifted or scattered into the Lyα resonance, they coupled the spin temperature of the 21 cm transition of hydrogen to the gas temperature, allowing it to deviate from the microwave background temperature. We show that the fluctuations in the radiation emitted by the first galaxies produced strong fluctuations in the 21 cm flux before the Lyα coupling became saturated. The fluctuations were caused by biased inhomogeneities in the density of galaxies, along with Poisson fluctuations in the number of galaxies. Observing the power spectra of these two sources would probe the number density of the earliest galaxies and the typical mass of their host dark matter halos. The enhanced amplitude of the 21 cm fluctuations from the era of Lyα coupling improves considerably the practical prospects for their detection.

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How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

1. S. Furlanetto
2. A. Mesinger
3. M. McQuinn
4. P. Hopkins
5. J. Pritchard
6. L. Hernquist
7. Renyue Cen
8. Abraham Loeb

Citations in the corpus

• Observational Constraints on Cosmic Reionization (2006, background): “These objects are capable of ionizing large volumes at high-redshift, and could have played an important role in the early reionization of the IGM, depending on their currently ill-constained space density (Panagia et al. 2005; Barkana & Loeb 2005c).”
• Cosmological Parameter Estimation Using 21 cm Radiation from the Epoch of Reionization (2005, background): “Recently, Barkana & Loeb (2005a) showed that redshift-space distortions from peculiar velocities allow for the decomposition of the observed 21 cm three-dimensional (3D) power spectrum into terms that are proportional to 0, 2, and 4, where is the cosine of the angle between a mode k and the line of…”
• 21cmfast: a fast, seminumerical simulation of the high‐redshift 21‐cm signal (2010, methodology): “(24) C© 2010 The Authors, MNRAS 411, 955–972 Monthly Notices of the Royal Astronomical Society C© 2010 RAS Downloaded from https://academic.oup.com/mnras/article-abstract/411/2/955/1273635 by guest on 30 July 2018 Following Barkana & Loeb (2005b), we truncate the sum at nmax = 23, and use their Popu”
• Wouthuysen-Field coupling strength and application to high-redshift 21-cm radiation (2005, background): “(54) The source emissivity is modeled following Barkana & Loeb (2005b) by the equation ǫ(ν, z) = ǫb(ν) Ωb mpΩm d dt ∫ f⋆(M, t)Mn(M, t)dM, (55) where M is the relevant halo mass, n(M, t) is the comoving number density of halos at proper time t per unit mass, f⋆(M, t) is the fraction of the baryons…”
• Inferring the astrophysics of reionization and cosmic dawn from galaxy luminosity functions and the 21-cm signal (2018, methodology): “21cmfast computes the Lyman series background from both X-ray excitation of HI and from direct stellar emission of photons in the Lyman bands, using the composite stellar spectra of Barkana & Loeb (2005).”
• Inhomogeneous recombinations during cosmic reionization (2014, background): “Nγ ≈ 4000 is expected for PopII stars (e.g. Barkana & Loeb 2005).”
• Charting the parameter space of the global 21-cm signal (2016, methodology): “We use the standard spectra of population II stars from Barkana & Loeb (2005b) (based on Leitherer et al. (1999)) to determine the spectrum and intensity of Lyα and LW photons, the strong LW feedback from Fialkov et al. (2013) (when LW feedback is applied), and the standard cosmological parameters…”
• 21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal (2015, result): “The choice of Nγ ≈ 4000 is expected from Population II stars (e.g. Barkana & Loeb 2005), while f? and fesc are extremely uncertain in high-z galaxies (e.g. Gnedin et al. 2008; Wise & Cen 2009; Ferrara & Loeb 2013), though our choices are consistent with observations of galaxy luminosity functions…”
• 21 cm cosmology in the 21st century (2011, methodology): “For convenience, we define a parameter controlling the normalization of the Lyα emissivity fα by setting the total number of Lyα photons emitted per baryon converted into stars as Nα = fαNα,ref where we take the reference values appropriate for normal (so-called, Population I and II) stars Nα,ref = ”
• The global 21-centimeter background from high redshifts (2006, methodology): “Cosmological measurements, spin temperature fluctuations (Barkana & Loeb 2005b; Pritchard & Furlanetto 2006), minihaloes (Iliev et al. 2002; Furlanetto & Oh 2006) and reionization itself must all be placed in their proper contexts, and this is a first step in that direction.”