National Astronomical Observatory of Japan

Subaru Telescope Detects the Sudden Appearance of Galaxies in the Early Universe


Formation of a Rich Galaxy Cluster 7 Billion Years Ago

The red blotch-like celestial objects at the centers of these 7 panels are 7 galaxies from 13.1 billion years ago discovered by the Subaru telescope. The galaxies are a kind known as Lyman α Emitters, abbreviated as LAE below. The galaxies shown here include the most distant object ever discovered by the Subaru Telescope. These are the fruits of installing a special NB101 filter, designed for hunting LAE galaxies, in Suprime-Cam and conducting a 106 hour observation plan, an extremely long time as Subaru Telescope observations go. This allowed us to survey the distant Universe (the Universe from 13.1 billion years ago) with an unprecedented high sensitivity.

A New View of the Universe from Unexpected Results

These observations expected to find dozens of LAE galaxies, but instead found only these 7. The observation team member said, "At first we were disappointed by the small number of LAE galaxies, but after thinking about it logically, we realized this was an exciting result. About 13.1 billion years ago, the number of LAE galaxies increased suddenly in the short period of only 0.1 billion years. "

These observational results revealed a new picture of the Universe. In the process of cosmic reionization, the neutral gas shrouding LAE galaxies rapidly disappeared about 13.1 billion years ago.

Text by: Masami Ouchi (The University of Tokyo, ICRR)
Translation by: Ramsey Lundock (NAOJ)

Image Data

ObjectSubaru/XMM Newton Deep Survey (SXDS) field (in the constellation Cetus) and the Cosmic Evolution Survey (COSMOS) field (in the constellation Sextans)
TelescopeThe Subaru Telescope
WavelengthNB101 (1.01 μm, shown in red), i (0.76 μm, green), B (0.45 μm, blue)
Exposure106 hr. (NB101), total combined exposure time for SXDS and COSMOS
DateDec. 2010, Jan. 2011, Dec. 2012, Feb. 2013
ObserverMasami Ouchi and the rest of the NB101 Survey Team
CreditThe University of Tokyo; National Astronomical Observatory of Japan


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