1st of December 2022 |
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Constraints on the cosmic dawn |
by Bevins et al. |
Understanding the early Universe, when the first stars and galaxies
formed (the "Cosmic Dawn"), is one of the major science goals of a number of new
observatories. The James Webb Space Telescope (JWST), for example,
will directly image these early galaxies in deep near-infrared
surveys.
Observations of the redshifted 21-cm line of atomic hydrogen have
provided several upper limits on the 21-cm power spectrum.
A tentative detection of the sky-averaged signal at redshift
z≈17, made with the Experiment to Detect the Global EoR Signature
(EDGES) low-band antenna, was reeported in 2018.
However,
this is yet to be confirmed.
SARAS 3 is a radiometer based on a monocone antenna that has made observations of the sky from a location in Southern India. The experiment is the first global 21-cm experiment of its kind to take observations while floating on a body of water, which is expected to improve the total efficiency of the antenna. Fifteen hours of observations were integrated in the frequency range 55–85 MHz (z≈15–25), reduced after radio frequency interference filtering, with corrections made for emission from the water beneath the antenna and receiver noise temperature. No evidence for an EDGES-like signal was seen, and the data were used to constrain a population of radio-luminous galaxies ~200 million years after the Big Bang. The results are presented in this week's issue of Nature Astronomy. (Image credit: https://arxiv.org/pdf/2104.03522.pdf) |