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29 March 2024
 
  » arxiv » 2004.0678

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Tight Constraints on the Excess Radio Background at $z = 9.1$ from LOFAR
R. Mondal ; A. Fialkov ; C. Fling ; I.T. Iliev ; R. Barkana ; B. Ciardi ; G. Mellema ; S. Zaroubi ; L.V.E Koopmans ; F. G. Mertens ; B. K. Gehlot ; R. Ghara ; A. Ghosh ; S. K. Giri ; V.N. Pandey ;
Date 1 Apr 2020
AbstractThe ARCADE2 and LWA1 experiments have claimed an excess over the Cosmic Microwave Background (CMB) at low radio frequencies. If the cosmological high-redshift contribution to this radio background is between 0.1% and 22% of the CMB at $1.42,$GHz, it could explain the tentative EDGES Low-Band detection of the anomalously deep absorption in the 21-cm signal of neutral hydrogen (Fialkov & Barkana 2019). We use the upper limit on the 21-cm signal from the Epoch of Reionization ($z=9.1$) based on $141,$hours of observations with LOFAR (Mertens et al. 2020) to evaluate the contribution of the high redshift Universe to the detected radio background. Marginalizing over astrophysical properties of star-forming halos, we find (at 68% C.L.) that the cosmological radio background can be at most 0.7% of the CMB at $1.42,$GHz. This limit rules out strong contribution of the high-redshift Universe to the ARCADE2 and LWA1 measurements. Even though LOFAR places limit on the extra radio background, excess of $0.1-0.7$% over the CMB (at $1.42,$GHz) is still allowed and could explain the EDGES Low-Band detection. We also constrain the thermal and ionization state of the gas at $z = 9.1$, and put limits on the properties of the first star-forming objects. We find that, in agreement with the limits from EDGES High-Band data, LOFAR data disfavour scenarios with inefficient X-ray sources and cases where the Universe was ionized by massive halos only.
Source arXiv, 2004.0678
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