Thermal and Resonant Emission of Dark Ages Halos in the Rotational Lines of HeH${}^{+}$

Abstract

We analyse the thermal emission and resonant scattering of CMB radiation from the dark ages halos in the rotational lines of the helium hydride ion (HeH${}^{+}$), one of the first chemical compounds in the Universe. Evaluating the optical depth, thermal and resonant brightness temperatures and spectral fluxes of dark ages halos is based on computing the cross-sections and rate coefficients of excitation/de-excitation of the lowest five rotational states of HeH${}^{+}$ by inelastic collisions with atomic hydrogen. It was shown that in the Dark Ages the collisional excitation/de-excitation by atoms of neutral hydrogen and electrons are competitive, whereas in the denser regions, e.g., in the halos, the contribution of collisions with atomic hydrogen is dominant. We demonstrate the peak-like time-dependence of halo luminosities in HeH${}^{+}$ lines.

13 pages, 9 figures, 9 tables; accepted for publication in Phys.Rev.D

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• First astrophysical detection of the helium hydride ion (HeH${}^{+}$)
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Cited by in corpus (6)

• Energy-transfer Quantum Dynamics of HeH${}^{+}$ with He atoms: Rotationally Inelastic Cross Sections and Rate Coefficients
• The first molecules in the intergalactic medium and halos of the Dark Ages and Cosmic Dawn
• Signal in the Hyperfine Structure Line of the Ground State of Atomic Hydrogen from the Dark Ages as a Cosmological Test
• Global signal in the redshifted hydrogen 21-cm line from the Dark Ages and Cosmic Dawn: Dependence on the nature of dark matter and modeling of first light
• On the Possibility of Detecting a Global Signal in the Line of the Hyperfine Structure of Hydrogen from the Dark Ages
• Distortion of the CMB spectrum by the first molecules of the Dark Ages