Constraint on primordial magnetic fields in the light of ARCADE 2 and EDGES observations

Pravin Kumar Natwariya

doi:10.1140/epjc/s10052-021-09155-z

Abstract

We study the constraints on primordial magnetic fields (PMFs) in the light of the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) low-band observation and Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission (ARCADE 2). ARCADE 2 observation detected extra-galactic excess radio radiation in the frequency range 3–90 GHz. The enhancement in the radio radiation is also supported by the first station of the Long Wavelength Array (LWA1) in the frequency range 40–80 MHz. The presence of early radiation excess over the cosmic microwave background can not be completely ruled out, and it may explain the EDGES anomaly. In the presence of decaying PMFs, 21 cm differential brightness temperature can modify due to the heating of the gas by decaying magnetic fields, and we can constraint the magnetic fields. For excess radiation fraction (A_r) to be LWA1 limit, we show that the upper bound on the present-day magnetic field strength, B_0, on the scale of 1 Mpc is lesssim 3.7 nG for spectral index n_B=-2.99. While for n_B=-1, we get B_0lesssim 1.1times 10^{-3} nG. We also discuss the effects of first stars on IGM gas evolution and the allowed value of B_0. For A_r to be LWA1 limit, we get the upper constraint on magnetic field to be B_0(n_B=-2.99)lesssim 4.9times 10^{-1} nG and B_0(n_B=-1)lesssim 3.7times 10^{-5} nG. By decreasing excess radiation fraction below the LWA1 limit, we get a more stringent bound on B_0.

Highlights

Tgas and TCMB varies with the redshift as ∝ (1 + z)2 and ∝ (1 + z) respectively, and temperatures of both the gas and cosmic microwave background radiation (CMBR) found to be ∼ 6.7 K and ∼ 49.1 K at the redshift z = 17 respectively
The enhancement in the background radiation is supported by the first station of the long wavelength array (LWA1) in frequency range 40–80 MHz, and it is modelled by a power law with a spectral index (β) of −2.58 ± 0.05 [14], while ARCADE 2 is modelled with β = −2.62 ± 0.04 [6,8]
Ambipolar diffusion of magnetic fields is important in neutral medium as it is inversely proportional to free-electron fraction (Xe) and Xe ∼ 10−4 after redshift z 100 [5,17,39]

Summary

Introduction

The contribution to the background radiation is assumed to be CMB radiation, the EDGES anomaly encouraged to develop the alternative models in which radio background enhanced [1,6,7]. The EDGES absorption signal can be explained by considering the possible early excess of radio radiation [6]. [42,43], the authors claim that thermal emission from the axion quark nugget dark matter model can explain the EDGES signal, and it can contribute a fraction of the radiation excess observed by ARCADE 2. [45], the authors consider accreting Pop III black holes and shows that radio emission from these sources can produce the EDGES like signal by increasing background radiation temperature. Authors consider a uniform redshift-independent synchrotron-like radiation, motivated by the ARCADE2 and LWA1 observations This model can explain the EDGES anomaly in addition to enhancement of cosmic down power spectrum. Heating rate per unit volume due to the ambipolar diffusion (Γambi) and turbulence decay (Γturb) is given by [5,17],

Evolution of the gas temperature in the presence of PMFs

Heating of the IGM due to background radiation

Findings

Result and discussion

Conclusions