Most Distant Galaxy in Cosmic Dawn Discovered

Color composite image of the Subaru XMM-Newton Deep Survey Field. Right panel: The red galaxy at the center of the image is the most distant galaxy, SXDF-NB1006-2. Left panels: Close-ups of the most distant galaxy. (NAOJ)

A team of Japanese astronomers has pinpointed the farthest known galaxy from Earth using the Subaru and Keck Telescopes.

Called SXDF-NB1006-2, the galaxy is 12.91 billion light-years away—slightly more remote than GN-108036, which was designated the most distant galaxy last year.

The researchers believe the object dates back to the final phase of the cosmic dawn or re-ionization period, about 200 to 500 million years after the alleged big bang. During this time, the first stars and galaxies formed, heating surrounding hydrogen gas with their burgeoning radiation and re-ionizing the universe.

The team surveyed extremely faint, potential galaxies at a redshift of nearly 7.3, and identified one with an emission line characteristic of a distant galaxy. Redshift is the change observed in the wavelength of light emitted from an object as it moves away from the observer. The higher the redshift number, the further away, and hence older, the object is.

They also found that the proportion of un-ionized hydrogen gas 12.91 billion years ago was higher than today. However, more galaxies from this epoch must be observed to understand the universe’s dark periods and the formation of the first generation of stars.

Once Subaru’s Hyper Suprime-Cam (HSC) is in place later this year, a field of view seven times greater will become visible, allowing large surveys of galaxies beyond a redshift of 7.

“By conducting an extremely wide HSC survey for distant galaxies beyond redshift 7, we will find the mechanisms of the cosmic re-ionization in a variety of ways, not just by investigating their number and brightness,” said researcher Takatoshi Shibuya at The Graduate University for Advanced Studies in a press release.

When the Thirty Meter Telescope (TMT) becomes available during the next decade, it will be able to detect faint light from galaxies up to a redshift of 14.

“We have been pushing the limits of 8-10 meter class telescopes to detect distant galaxies,” said researcher Masanori Iye, leader of the TMT project at the National Astronomical Observatory of Japan, in the release.

“… The day is not so far off when the mysteries of the dark ages of the universe and the physical properties of the first galaxies will be revealed.”

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• Toasting Life

  I would be interested in a basic mathematical comparison between the redshift distance and the  light-year distance, to better understand the relationship. Thanks for this article.