# Experiment to Detect the Global EoR Signature

Alternative names EDGES Murchison Radio-astronomy Observatory Australia 26°41′50″S 116°38′21″E﻿ / ﻿26.69719°S 116.63903°E Radio telescope www.haystack.mit.edu/ast/arrays/Edges/ Location of Experiment to Detect the Global EoR Signature

The Experiment to Detect the Global EoR Signature (EDGES) is an experiment and radio telescope located in a radio quiet zone at the Murchison Radio-astronomy Observatory in Western Australia. It is a collaboration between Arizona State University and Haystack Observatory, with infrastructure provided by CSIRO.[1] EoR stands for epoch of reionization, a time in cosmic history when neutral atomic hydrogen gas became ionised due to ultraviolet light from the first stars.

## Low-band instruments

The experiment has two low-band instruments, each of which has a dipole antenna pointed to the zenith and observing a single polarisation.[2] The antenna is around 2 by 1 metre (6.6 ft × 3.3 ft) in size, sat on a 30 by 30 metres (98 ft × 98 ft) ground shield. It is coupled with a radio receiver, with a 100m cable run to a digital spectrometer.[1] The instruments operate at 50–100 MHz (6.0–3.0 m), and are separated by 150m. Observations started in August 2015.[2]

### 78 MHz absorption profile

In March 2018 the collaboration published a paper in Nature announcing the discovery of a broad absorption profile centered at a frequency of ${\displaystyle 78\pm 1}$MHz in the sky-averaged signal after subtracting Galactic synchrotron emission. The absorption profile has a width of ${\displaystyle 19_{-2}^{+4}}$MHz and an amplitude of ${\displaystyle 0.5_{-0.2}^{+0.5}}$K, against a background RMS of 0.025K, giving it a signal-to-noise ratio of 37. The equivalent redshift is centered at ${\displaystyle z\approx 17}$, spanning z=20–15. The signal is possibly due to ultraviolet light from the first stars in the Universe altering the emission of the 21cm line. A "more exotic scenario" is that the signal is due to interactions between dark matter and baryons.[2][3]

## High-band instruments

The high-band instrument is of similar design, and operates at 90–200 MHz (3.3–1.5 m).[2]

## References

1. ^ a b "MIT Haystack Observatory: EDGES". www.haystack.mit.edu. Retrieved 2 March 2018.
2. ^ a b c d Bowman, Judd D.; Rogers, Alan E. E.; Monsalve, Raul A.; Mozdzen, Thomas J.; Mahesh, Nivedita (1 March 2018). "An absorption profile centred at 78 megahertz in the sky-averaged spectrum". Nature. 555 (7694): 67–70. arXiv:1810.05912. Bibcode:2018Natur.555...67B. doi:10.1038/nature25792. ISSN 1476-4687. PMID 29493587.
3. ^ Barkana, Rennan (1 March 2018). "Possible interaction between baryons and dark-matter particles revealed by the first stars". Nature. 555 (7694): 71–74. arXiv:1803.06698. Bibcode:2018Natur.555...71B. doi:10.1038/nature25791. ISSN 1476-4687. PMID 29493590.