Keck/NAOJ: Oldest Galaxy Protocluster Forms "Queen's Court"

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Oldest Galaxy Protocluster Forms "Queen's Court"
W.M. Keck Observatory | National Astronomical Observatory of Japan | 2019 Sep 27

The most distant protocluster discovered by the Subaru Telescope. The blue shading shows the calculated extent of the protocluster, and the bluer color indicates higher density of galaxies in the protocluster. The red objects in zoom-in figures are the 12 galaxies found in it. This figure shows a square field-of-view 24 arcminutes along each side (corresponding to 198 million light-years along each side at a distance of 13 billion light-years). Each zoom-in figure is 16 arcseconds along each side (corresponding to 2.2 million light-years). (Credit: NAOJ/Harikane et al)

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Using multiple Maunakea Observatories – the Subaru Telescope, W. M. Keck Observatory, and Gemini Observatory – an international team of astronomers has discovered the earliest protocluster ever found; it is comprised of a collection of 12 galaxies in the constellation Cetus, which were observed as they were about 13 billion years ago. One of the 12 galaxies is a giant object known as Himiko, which was discovered a decade ago by the Subaru Telescope and named for a legendary queen in ancient Japan. This discovery suggests that large structures such as protoclusters already existed when the universe was only about 800 million years old – 6 percent of its present age.

In the present universe, galaxy clusters can contain thousands of members, but how these clusters form is a big question in astronomy. To understand the formation of clusters, astronomers search for possible progenitors in the ancient universe, known as protoclusters. A protocluster is a dense system of dozens of galaxies in the early universe, growing into a cluster. The previous record holder was the SDF protocluster, discovered by the Subaru Telescope in the Subaru Deep Field (SDF) near the constellation Coma Berenices. ...

In the map of the universe made by the Subaru Telescope, the team discovered a protocluster candidate, z66OD, where galaxies are 15 times more concentrated than normal for that era. The team then conducted follow-up spectroscopic observations using Keck Observatory’s DEep Imaging and Multi-Object Spectrograph (DEIMOS) as well as Gemini North telescope’s Gemini Multi-Object Spectrograph (GMOS) to confirm the 12 galaxies existed 13 billion years ago, making the protocluster the earliest one known to date. ...

Record-Breaking Protocluster Takes Fast-track
Gemini Observatory | 27 Sep 2019

SILVERRUSH. VIII. Spectroscopic Identifications of Early Large Scale Structures with Protoclusters
Over 200 Mpc at z~6-7: Strong Associations of Dusty Star-Forming Galaxies ~ Yuichi Harikane et al

• arXiv.org > astro-ph > arXiv:1902.09555 > 25 Feb 2019 (v1), 24 Jun 2019 (v2)