Subaru Telescope | National Astronomical Observatory, Japan | 2014 Nov 18
A team of astronomers using the Subaru Telescope's Suprime-Cam to perform the Subaru Ultra-Deep Survey for Lyman-alpha Emitters have looked back more than 13 billion years to find 7 early galaxies that appeared quite suddenly within 700 million years of the Big Bang. The team, led by graduate student Akira Konno and Dr. Masami Ouchi (Associate Professor at the University of Tokyo's ICRR) was looking for a specific kind of galaxy called a Lyman-alpha emitter (LAE), to understand the role such galaxies may have played in an event called "cosmic reionization".
Color composite images of seven LAEs found in this study as they appeared 13.1 billion
years ago. This represents the combination of three filter images from Subaru Telescope.
Red objects between two white lines are the LAEs. The LAEs of 13.1 billion years ago
have a quite red color due to the effects of cosmic expansion on their component
wavelengths of light. (Credit: ICRR, University of Tokyo; NAOJ)
LAE galaxies are illuminated by strong hydrogen excitation (called Lyman-alpha emission). The team’s discovery of these LAEs at a distance of 13.1 billion light-years suggests that LAE galaxies appeared rather suddenly in the early universe.
The universe was born in the Big Bang some 13.8 billion years ago. In its earliest epochs, it was filled with a hot “soup” of charged protons and electrons. As the newborn universe expanded, its temperature decreased uniformly. When the universe was 400,000 years old, conditions were cool enough to allow the protons and electrons to bond and form neutral hydrogen atoms. That event is called “recombination” and resulted in a universe filled with a “fog” of these neutral atoms.
Eventually the first stars and galaxies began to form, and their ultraviolet light ionized (energized) the hydrogen atoms, and “divided” the neutral hydrogen into protons and electrons again. As this occurred, the “fog” of neutrals cleared. Astronomers call this event “cosmic reionization” and think that it ended about 12.8 billion years ago (about a billion years after the Big Bang). The timing of this event -- when it started and how long it lasted -- is one of the big questions in astronomy.
To investigate this cosmic reionization, the Subaru team searched for early LAE galaxies at a distance of 13.1 billion light-years. Although Hubble Space Telescope has found more distant LAE galaxies, the discovery of seven such galaxies at 13.1 billion light-years represents a distance milestone for Subaru Telescope. ...
Accelerated Evolution of Lyα Luminosity Function at z≳7 Revealed by the Subaru Ultra-Deep Survey for Lyα Emitters at z=7.3 - Akira Konno et al
- arXiv.org > astro-ph > arXiv:1404.6066 > 24 Apr 2014 (v1), 19 Sep 2014 (v2)