Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 0808.1461

Influence of primordial magnetic fields on 21 cm emission

Dominik R. G. Schleicher·Robi Banerjee·Ralf S. Klessen
View original source ↗Read source document ↗Export metadata ↓

Abstract

Magnetic fields in the early universe can significantly alter the thermal evolution and the ionization history during the dark ages. This is reflected in the 21 cm line of atomic hydrogen, which is coupled to the gas temperature through collisions at high redshifts, and through the Wouthuysen-Field effect at low redshifts. We present a semi-analytic model for star formation and the build-up of a Lyman alpha background in the presence of magnetic fields, and calculate the evolution of the mean 21 cm brightness temperature and its frequency gradient as a function of redshift. We further discuss the evolution of linear fluctuations in temperature and ionization in the presence of magnetic fields and calculate the effect on the 21 cm power spectrum. At high redshifts, the signal is increased compared to the non-magnetic case due to the additional heat input into the IGM from ambipolar diffusion and the decay of MHD turbulence. At lower redshifts, the formation of luminous objects and the build-up of a Lyman alpha background can be delayed by a redshift interval of 10 due to the strong increase of the filtering mass scale in the presence of magnetic fields. This tends to decrease the 21 cm signal compared to the zero-field case. In summary, we find that 21 cm observations may become a promising tool to constrain primordial magnetic fields.

Explore related subjects

astro-ph

Keep this discovery

BibTeXRIS

Dominik R. G. Schleicher, Robi Banerjee, Ralf S. Klessen. 2008-12-17. Influence of primordial magnetic fields on 21 cm emission. https://doi.org/10.1088/0004-637x%2F692%2F1%2F236

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2018

The Outward Radial Offset of Neptune Ring Arcs

The designation of the customary restricted three-body disturbing potential $Φ$ as the perturbation Hamiltonian is believed to be the cause of Neptune ring arcs' radial offset between theories and observations. To identify the appropriate perturbation Hamiltonian, the energy integral in the fixed frame of a restricted three-body system, consisting of the central, primary, and test bodies, is reconsidered. It is shown that the perturbation energy includes the disturbing potential $Φ$ and the potential arising from the angular momentum terms of the test body. Both potentials happen to be singular as the test body goes to infinity contradicting to the perturbation nature. These two potentials can be combined to an energy relevant disturbing potential $Φ^{*}=βΦ$ which is regular at infinity because of the cancellation of the singularities. For circular orbits of the primary, the energy equation is conservative, and $Φ^{*}$ is identified as the perturbation Hamiltonian. Applying this result to evaluate the backgrund effect of Triton to the arc-Galatea system of Neptune, it is shown that there is a small difference $ΔΦ=(Φ^{*}-Φ)$ which amounts to an outward radial offset of the corotation location of Galatea by 0.3 Km. The mismatch between the pattern speed of Galatea's corotation potential and the mean motion velocity of the arcs could be resolved by considering the finite mass of Fraternite. However, by using $Φ^{*}$, Galatea's eccentricity could be reassessed in terms of the mass of Fraternite.

astro-ph↗
arXiv2018

Nuclear Reaction Network for Primordial Nucleosynthesis: a detailed analysis of rates, uncertainties and light nuclei yields

We analyze in details the standard Primordial Nucleosynthesis scenario. In particular we discuss the key theoretical issues which are involved in a detailed prediction of light nuclide abundances, as the weak reaction rates, neutrino decoupling and nuclear rate modeling. We also perform a new analysis of available data on the main nuclear processes entering the nucleosynthesis reaction network, with particular stress on their uncertainties as well as on their role in determining the corresponding uncertainties on light nuclide theoretical estimates. The current status of theoretical versus experimental results for 2H, 3He, 4He and 7Li is then discussed using the determination of the baryon density as obtained from Cosmic Microwave Background anisotropies.

astro-ph↗
arXiv2018

Sky coverage of orbital detectors. Analytical approach

Orbital detectors without pointing capability have to keep their field of view axis laying on their orbital plane, to observe the largest sky fraction. A general approach to estimate the exposure of each sky element for such detectors is a valuable tool in the R&D phase of a project, when the detector characteristics are still to be fixed. An analytical method to estimate the sky exposure is developed, which makes only few very reasonable approximations. The formulae obtained with this method are used to compute the histogram of the sky exposure of a hypothetical gamma-ray detector installed on the ISS. The C++ code used in this example is freely available on the https://github.com/dcasadei/SkyCoverage web page.

astro-ph↗