Constraint on Primordial Magnetic Fields In the Light of ARCADE 2 and EDGES Observations

We study the constraints on primordial magnetic fields (PMFs) in the light of Experiment to Detect the Global Epoch of Reionization Signature (EDGES) low-band observation and Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission (ARCADE 2). In the presence of PMFs, 21 cm differential brightness temperature can modify due to the heating of the gas by decaying magnetic fields. ARCADE 2 observation detected excess radio radiation in the frequency range 3-90 GHz. Using the ARCADE 2 and EDGES observations, we find the upper constraint, at the length scale of 1 Mpc, on the primordial magnetic field $B_{\rm 1~Mpc}\lesssim 53.3$ pG for the nearly scale-invariant PMFs using 10% of observed excess radio radiation. However, taking into account the heating effects due to x-ray and VDKZ18 (Venumadhav et al. 2018), the upper constraint on the strength of the primordial magnetic fields can further be lowered to $B_{\rm 1~Mpc}\lesssim37$ pG.Comment: 7 pages, 4 figures, Heating effects due to x-ray and VDKZ18 adde

Viscosity in cosmic fluids

The effective theory of large-scale structure formation based on $\Lambda$CDM paradigm predicts finite dissipative effects in the resulting fluid equations. In this work, we study how viscous effect that could arise if one includes self-interaction among the dark-matter particles combines with the effective theory. It is shown that these two possible sources of dissipation can operate together in a cosmic fluid and the interplay between them can play an important role in determining dynamics of the cosmic fluid. In particular, we demonstrate that the viscosity coefficient due to self-interaction is added inversely with the viscosity calculated using effective theory of $\Lambda$CDM model. Thus the larger viscosity has less significant contribution in the effective viscosity. Using the known bounds on $\,\sigma/m$ for self-interacting dark-matter, where $\,\sigma\,$ and $m$ are the cross-section and mass of the dark-matter particles respectively, we discuss role of the effective viscosity in various cosmological scenarios.Comment: 7 pages, Updated to match with the published versio

Rotating Scalar Field and Formation of Bose Stars

We study numerical evolutions of an initial cloud of self-gravitating bosonic dark matter with finite angular momentum and self-interaction in kinetic regime. It is demonstrated that such a system can undergo gravitational condensation and form a Bose star. The results show that the gravitational condensation time is strongly influenced by the presence of finite angular momentum or the strength of self-interaction. We find that in the cases related with attractive or no self-interaction, there is no significant transfer of angular momentum from the initial cloud to the formed star. However, for the case repulsive interaction our results indicate that such a angular-momentum transfer is possible. These results are consistent with the earlier analytical work where the stability of the rotating boson star was considered [Dmitriev et al. 2021].Comment: New results have been incorporate

In Search of Global 21-cm Signal using Artificial Neural Network in light of EDGES and ARCADE 2

Understanding the astrophysical nature of the first stars still remains an unsolved problem in cosmology. The redshifted global 21-cm signal and power spectrum act as a treasure trove to probe the Cosmic Dawn era -- when the intergalactic medium was mostly neutral. Many experiments, like SARAS 3, SKA, EDGES, DARE, etc., have been proposed to probe the cosmic dawn era. However, extracting the faint cosmological signal buried inside the brighter foregrounds $\mathcal{O}(10^4)$ remains challenging. Considering the excess radio background, we have constructed all possible $T_{21}$ signals in the EDGES limit. We have used a single Artificial Neural Network for $T_{21}$ parameter extraction in the presence of the foreground and noise with Root Mean Square Error (RMSE) and R-Squared (R2) score of $(0.2 - 0.08)$ and $(0.66 - 0.94)$, respectively. Here, we also explore the parameter estimation in the presence of heating of intergalactic medium due to background radio radiation mediated by Ly$\alpha$ photons from first stars, and we found that the effect indeed has a significant impact on parameters correlation and their estimation.Comment: 13 pages, 47 figures, 1 tabl

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

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 $$B_0\lesssim 1.1\times 10^{-3}$$ 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 $$B_0(n_B=-2.99)\lesssim 4.9\times 10^{-1}$$ nG and $$B_0(n_B=-1)\lesssim 3.7\times 10^{-5}$$ nG. By decreasing excess radiation fraction below the LWA1 limit, we get a more stringent bound on $$B_0$$

Baryon-Dark matter interaction in presence of magnetic fields in light of EDGES signal

The Experiment to Detect the Global Epoch of reionization Signature (EDGES) collaboration has reported an excess absorption dip in the 21 cm signal during cosmic dawn era. The stronger than expected 21 absorption signal indicates that gas was much cooler than the standard cosmological prediction. The observed 21-cm signal can be explained by decreasing the gas temperature via baryon-DM interaction. In this work, we study the temperature evolution of the gas and Dark Matter (DM) in the presence of magnetic fields. The magnetic heating via ambipolar diffusion and the turbulent decay increases both the gas and DM temperature at low redshift and this heating is more in the favour of baryons compared to DM. In the presence of strong magnetic field, a large baryon-DM interaction cross section is required to balance magnetic heating to explain the EDGES signal as compared to weak magnetic field. We also study the brightness temperature during the cosmic dawn era and put constraint on the strength of the magnetic field for a particular mass and baryon-DM cross section.by Jitesh R. Bhatt, Pravin Kumar Natwariya, Alekha C. Nayak and Arun Kumar Pande