{
  "id": "2103.04241",
  "version": "v1",
  "published": "2021-03-07T02:56:21.000Z",
  "updated": "2021-03-07T02:56:21.000Z",
  "title": "The Anomalous 21-cm Absorption at High Redshifts",
  "authors": [
    "Fulvio Melia"
  ],
  "comment": "9 pages, 1 figure. Accepted for publication in EPJ-C",
  "categories": [
    "astro-ph.CO"
  ],
  "abstract": "The EDGES collaboration has reported the detection of a global 21-cm signal with a plateau centered at 76 MHz (i.e., redshift 17.2), with an amplitude of 500^(+200)_(-500) mK. This anomalous measurement does not comport with standard cosmology, which can only accommodate an amplitude < 230 mK. Nevertheless, the line profile's redshift range (15 < z < 20) suggests a possible link to Pop III star formation and an implied evolution out of the `dark ages.' Given this tension with the standard model, we here examine whether the observed 21-cm signal is instead consistent with the results of recent modeling based on the alternative Friedmann-Lemaitre-Robertson-Walker cosmology known as the R_h=ct universe, showing that--in this model--the CMB radiation might have been rethermalized by dust ejected into the IGM by the first-generation stars at redshift z < 16. We find that the requirements for this process to have occurred would have self-consistently established an equilibrium spin temperature T_s~3.4 K in the neutral hydrogen, via the irradiation of the IGM by deep penetrating X-rays emitted at the termination shocks of Pop III supernova remnants. Such a dust scenario has been strongly ruled out for the standard model, so the spin temperature (~3.3 K) inferred from the 21-cm absorption feature appears to be much more consistent with the R_h=ct profile than that implied by LCDM, for which adiabatic cooling would have established a spin temperature T_s(z=17.2)~6 K.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-03-07T02:56:21.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "high redshifts",
      "line profiles redshift range",
      "standard model",
      "absorption feature appears",
      "equilibrium spin temperature"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 9,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}