Hydrogen Molecules in the Dark Ages Halos: Thermal Emission vs. Resonant Scattering

Abstract

The emission from dark ages halos in the lines of transitions between lowest rotational levels of hydrogen and hydrogen deuteride molecules is analyzed. It is assumed molecules to be excited by CMB and collisions with hydrogen atoms. The physical parameters of halos and number density of molecules are precalculated in assumption that halos are homogeneous top-hat spheres formed from the cosmological density perturbations in the four-component Universe with post-Planck cosmological parameters. The differential brightness temperatures and differential spectral fluxes in the rotational lines of H${}_2$-HD molecules are computed for two phenomena: thermal luminescence and resonant scattering of CMB radiation. The results show that expected maximal values of differential brightness temperature of warm halos ($T_K\sim$200-800 K) are at the level of nanokelvins, are comparable for both phenomena, and are below sensitivity of modern sub-millimeter radio telescopes. For hot halos ($T_K\sim$2000-5000 K) the thermal emission of H2-ortho molecules dominates and the differential brightness temperatures are predicted to be of a few microkelvins at the frequencies 300-600 GHz, that could be detectable with telescopes of a new generation.

18 pages, 9 figures, 16 tables; accepted for publication in ApJ; in the revised version the discussion about impact of new coefficients of collision excitation H2-H on the brightness temperature as well as the comparison with results of other authors are added

References in corpus (4)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• Observational constraints on Cosmic Reionization
• Spectral Spatial Fluctuations of CMBR: Strategy and Concept of the Experiment
• HD molecule and search for early structure-formation signatures in the Universe

Cited by in corpus (8)

• The first molecules in the intergalactic medium and halos of the Dark Ages and Cosmic Dawn
• Thermal and Resonant Emission of Dark Ages Halos in the Rotational Lines of HeH${}^{+}$
• Mapping the Universe in HD
• 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
• Sensitivity of the redshifted 21 cm signal from the Dark Ages to parameters of primordial magnetic fields
• Global Signals of the First Molecules from the Dark Ages in the Presence of Primordial Magnetic Fields