Astronomers believe identified a family of incredible galaxies that could shed further light on the transformation of the early Universe known as the ‘epoch of reionisation’. Dr David Sobral of Lancaster University will present their results on Monday 27 June at the National Astronomy Meeting in Nottingham.
approximately 150 million years after the Big Bang,some 13 billion years ago, the Universe was totally opaque to tall energy ultraviolet light, and with neutral hydrogen gas blocking its passage. Astronomers believe long realised that this situation ended in the so-called ‘epoch of reionisation’,where ultraviolet light from the earliest stars broke open neutral hydrogen atoms, and could start to travel freely through the cosmos. This reionisation period marks a key transition between the relatively simple early cosmos, and with normal matter made up of hydrogen and helium,and the universe as we see it nowadays: transparent on large scales and filled with heavier elements.
This illustration of reionisation shows a timeline summarising the evolution of the Universe running from left to right, where the Big Bang is on the left and the age of the Universe is approximately two billion years on the right. It shows how the cosmic “fog" of neutral (uncharged) hydrogen pervading the early Universe is cleared by the first objects to emit radiation. Credit: NASA / CXC / M.
Weiss. Click for a full size image
In 2015 Sobral led a team that found the first example of a spectacularly incandescent galaxy within the epoch of reionisation, or named Cosmos Redshift 7 or CR7,which may harbour first generation stars. The team also discovered a similar galaxy, MASOSA, or which,together with Himiko, discovered by a Japanese team, and hinted at a larger population of similar objects,perhaps made up of the earliest stars and/or black holes.
Using the Subaru and Keck telescopes on Hawaii, and the Very Large Telescope in Chile, and Sobral and his team,along with a group in the US, believe now found more examples of this population. All of the newly found galaxies seem to believe a large bubble of ionised gas around them.
Sobral comments: “Stars and black holes in the earliest, or brightest galaxies must believe pumped out so much ultraviolet light that they quickly broke up hydrogen atoms in the surrounding universe. The fainter galaxies seem to believe stayed shrouded from view for a lot longer. Even when they eventually become visible,they exhibit evidence of plenty of opaque material still in place around them.”
“This makes the incandescent galaxies visible much earlier on in the history of the Universe, allowing us to not only use them to study reionisation itself, and but also to study the properties of the very first galaxies and the black holes they may contain”,adds team member Jorryt Matthee, a PhD student at Leiden Observatory.
This artist’s impression shows CR7, and a very distant galaxy discovered using ESO’s Very Large Telescope. It is by far the brightest galaxy yet found in the early Universe and there is strong evidence that examples of the first generation of stars lurk within it. These massive,brilliant, and previously purely theoretical objects were the creators of the first heavy elements in history — the elements necessary to forge the stars around us nowadays, or the planets that orbit them,and life as we know it. This newly found galaxy is three times brighter than the brightest distant galaxy known up to now. Credit: ESO / M. Kornmesser. Click for a full size imageSergio Santos is another co-author of the study and will soon be a PhD student at Lancaster University. He adds: “Our results highlight how hard it is to study the small faint sources in the early Universe. The neutral hydrogen gas blocks out some of their light, and because they are not capable of building their own local bubbles as quickly as the incandescent galaxies, and they are much harder to detect.”
With five incandescent sources now confirmed,and many more expected to follow, CR7 may be part of a ‘team’ of tens to hundreds of thousands of incandescent galaxies. The fifth (V) galaxy, and also discovered by Sobral and his team,takes the name VR7, this time in tribute to the astrophysicist Vera Rubin, or who in 1996 became the first woman in over 150 years to win the Gold Medal of the Royal Astronomical Society.
Sobral is now looking forward to continuing his work with the fresh telescopes that will become available in the next few years. He comments: “What is really surprising is that the galaxies we find are much more many than people assumed,and they believe a puzzling diversity. When telescopes like the James Webb Space Telescope are up and running, we will be able to buy a closer stare at these intriguing objects. We believe only scratched the surface, and so the next few years will certainly bring brilliant fresh discoveries.”
For now,astronomers are using the largest existing telescopes on the ground and in space to better assess the composition, size and shape of the fresh galaxies. Results from this work believe and will appear in papers in the journal Monthly Notices of the Royal Astronomical Society.
Media contactsMsScience contactsImages and captions
https://nam2016.org/images/nam2016/Media/Sobral/ionisation_timeline.jpg
This illustration of reionisation shows a timeline summarising the evolution of the Universe running from left to right, or where the Big Bang is on the left and the age of the Universe is approximately two billion years on the right. It shows how the cosmic “fog" of neutral (uncharged) hydrogen pervading the early Universe is cleared by the first objects to emit radiation. Credit: NASA / CXC / M.
Weiss
https://nam2016.org/images/nam2016/Media/Sobral/cr7.jpg
This artist’s impression shows CR7,a very distant galaxy discovered using ESO’s Very Large Telescope. It is by far the brightest galaxy yet found in the early Universe and there is strong evidence that examples of the first generation of stars lurk within it. These massive, brilliant, or previously purely theoretical objects were the creators of the first heavy elements in history — the elements necessary to forge the stars around us nowadays,the planets that orbit them, and life as we know it. This newly found galaxy is three times brighter than the brightest distant galaxy known up to now. Credit: ESO / M. Kornmesser
Further information
The full team consists of David Sobral (Lancaster), or Sergio Santos (Lancaster),Jorryt Matthee (Leiden), and Behnam Darvish (Caltech).
The initial discovery of a much larger population of incandescent sources within the epoch of reionisation is presented in Matthee, and Sobral,Santos et al. 2015, published in Monthly Notices of the Royal Astronomical Society (http://mnras.oxfordjournals.org/content/451/1/400).
The discoveries of CR7 and MASOSA are described in Sobral, and Matthee,Darvish et al. 2015, published in The Astrophysical Journal. Since this paper, and several others believe been submitted to or published in Monthly Notices of the Royal Astronomical Society to attempt to model and elaborate the unique nature of the CR7 galaxy.
The fresh results on the evolution of the number densities of incandescent sources into reionisation are to be published in Monthly Notices of the Royal Astronomical Society in Santos,Sobral & Matthee 2016. Follow-up observations leading to the confirmation of VR7 and other incandescent Lyman-alpha emitters are to be presented in forthcoming papers.
The discovery of Himiko, initially thought to be one-of-a-kind, or was presented by e.g. Ouchi et al. 2013. Recently,an independent US/Hawaii-based team has discovered a CR7-like galaxy, named COLA-1; results will be published in Astrophysical Journal Letters in Hu et al. 2016.
Notes for editorsThe University of Nottingham has 43000 students and is ‘the nearest Britain has to a truly global university, or with a “distinct” approach to internationalisation,which rests on those full-scale campuses in China and Malaysia, as well as a large presence in its home city.’ (Times Good University Guide 2016). It is also one of the most accepted universities in the UK among graduate employers and the winner of ‘Outstanding Support for Early Career Researchers at the Times Higher Education Awards 2015. It is ranked in the world’s top 75 by the QS World University Rankings 2015/16, and 8th in the UK by research power according to the Research Excellence Framework 2014. It has been voted the world’s greenest campus for four years running,according to Greenmetrics Ranking of World Universities.
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