New record: Keck Observatory measures most distant galaxy

August 6, 2015 by Steve Jefferson
EGSY8p7 is the most distant confirmed galaxy whose spectrum obtained with the W. M. Keck Observatory places it at a redshift of 8.68 at a time when the Universe was less than 600 million years old. The illustration shows the remarkable progress made in recent years in probing early cosmic history. Such studies are important in understanding how the Universe evolved from an early dark period to one when galaxies began to shine. Hydrogen emission from EGSY8p7 may indicate it is the first known example of an early generation of young galaxies emitting unusually strong radiation. Credit: Adi Zitrin, California Institute Of Technology, 2015

A team of astrophysicists using the W. M. Keck Observatory in Hawaii has successfully measured the farthest galaxy ever recorded and more interestingly, captured its hydrogen emission as seen when the Universe was less than 600 million years old. Additionally, the method in which the galaxy called EGSY8p7 was detected gives important insight into how the very first stars in the Universe lit-up after the Big Bang. The paper will be published shortly in the Astrophysical Journal Letters.

Using Keck Observatory's powerful infrared spectrograph called MOSFIRE, the team dated the galaxy by detecting its Lyman-alpha emission line – a signature of hot hydrogen gas heated by strong ultraviolet emission from newly born stars. Although this is a frequently detected signature in galaxies close to Earth, the detection of Lyman-alpha emission at such a great distance is unexpected as it is easily absorbed by the numerous hydrogen atoms thought to pervade the space between galaxies at the dawn of the Universe. The result gives new insight into `cosmic reionization', the process by which dark clouds of hydrogen were split into their constituent protons and electrons by the first generation of galaxies.

"We frequently see the Lyman-alpha emission line of hydrogen in nearby objects as it is one of most reliable tracers of star-formation," said California Institute of Technology (Caltech) astronomer, Adi Zitrin, lead author of the discovery paper. "However, as we penetrate deeper into the Universe, and hence back to earlier times, the space between galaxies contains an increasing number of dark clouds of hydrogen which absorb this signal."

Recent work has found the fraction of galaxies showing this prominent line declines markedly after when the Universe was about a billion years old, which is equivalent to a redshift of about 6. Redshift is a measure of how much the Universe has expanded since the light left a distant source and can only be determined for faint objects with a spectrograph on a powerful large telescope such as the Keck Observatory's twin 10-meter telescopes, the largest on Earth.

"The surprising aspect about the present discovery is that we have detected this Lyman-alpha line in an apparently faint galaxy at a redshift of 8.68, corresponding to a time when the Universe should be full of absorbing hydrogen clouds," said co-author and Caltech astronomer Richard Ellis. "Quite apart from breaking the earlier record redshift of 7.73, also obtained at the Keck Observatory, this detection is telling us something new about how the Universe evolved in its first few hundred million years."

Computer simulations of cosmic reionization suggest the Universe was fully opaque to Lyman-alpha radiation in the first 400 million years of cosmic history and then gradually, as the first galaxies were born, the intense ultraviolet radiation from their young stars, burned off this obscuring hydrogen in bubbles of increasing radius which, eventually, overlapped so the entire space between galaxies became `ionized', that is composed of free electrons and protons. At this point the Lyman-alpha radiation was free to travel through space unimpeded.

It may be that the galaxy we have observed, EGSY8p7, which is unusually (intrinsically) luminous, has special properties that enabled it to create a large bubble of ionized much earlier than is possible for more typical galaxies at these times," said Sirio Belli, a Caltech graduate student who helped undertake the key observations. "EGSY8p7 was found to be both luminous and at high redshift, and its colors measured by the Hubble and Spitzer Space Telescopes indicate it may be powered by a population of unusually hot stars." 

Because the discovery of such an early source with powerful Lyman-alpha is somewhat unexpected, it provides new insight into the manner by which contributed to the process of reionization. Conceivably the process is patchy with some regions of space evolving faster than others, for example due to variations in the density of matter from place to place. Alternatively, EGSY8p7 may be the first example of an early generation which unusually strong ionizing radiation.

"In some respects, the period of cosmic reionization is the final missing piece in our overall understanding of the evolution of the Universe," says Zitrin. "In addition to pushing back the frontier to a time when the Universe was only 600 million years old, what is exciting about the present discovery is that the study of sources such as EGSY8p7 will offer new insight into how this process occurred."

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Tuxford
2.1 / 5 (14) Aug 06, 2015
...what is exciting about the present discovery is that the study of sources such as EGSY8p7 will offer new insight into how this process occurred


Same boilerplate language code for: "we really have no clue".
Hyperfuzzy
1.8 / 5 (15) Aug 06, 2015
A discussion on the absurdity that man knows how the universe began.
setnom
4.8 / 5 (13) Aug 06, 2015
A discussion on the absurdity that man knows how the universe began.


Not really. This galaxy was discovered 600 million years after the Big Bang. If anything, it's a discussion about the evolution of the Universe, not its formation.
Benni
1 / 5 (7) Aug 06, 2015
If anything, it's a discussion about the evolution of the Universe, not its formation.
What's the differences between "evolution" & "formation"?
setnom
5 / 5 (9) Aug 06, 2015
If anything, it's a discussion about the evolution of the Universe, not its formation.
What's the differences between "evolution" & "formation"?


Formation tries to explain how the Universe began. It lasts but a moment. Evolution deals with much larger timescales - billions of years. How, after the Big Bang, the Universe expanded and developed into what it is today. And, maybe, try and predict its future.

In case I wasn't clear, here's a picture, hehehe: http://i.imgur.com/zTaeLbb.png

For example, take the life a human being.
- "Formation" tells the story of how a child was born (picture the moment of a mother giving birth to the baby).
- "Evolution" tells the story of how that baby grew into an adult. Picture how the baby grew into a small child, all the events of his young life (going to school, having a girlfriend) and then into an adult (going to college, finding work, getting married, raising his kids, dying of old age).
Andrew Palfreyman
5 / 5 (6) Aug 07, 2015
A discussion on the absurdity that man knows how the universe began.

Behold the poor religionoid! - deluded into thinking that the scratch-marks left by bronze-age neolithic sheepshaggers in any way contribute to a discussion of early galaxies.
jsdarkdestruction
5 / 5 (4) Aug 07, 2015
A discussion on the absurdity that man knows how the universe began.

Why is it absurd to you?
enginarc
2 / 5 (4) Aug 07, 2015
Unless earth is at the center of the universe, in fact at the exact location where the big bang occurred, we shouldn't be comparing the age of the universe with a time calculated from a red shift between two objects in space.

It is not quite accurate to say the universe was 600m years old in this case.

Am I wrong? Can someone clarify for a nonscientist.
jsdarkdestruction
5 / 5 (4) Aug 07, 2015
Unless earth is at the center of the universe, in fact at the exact location where the big bang occurred, we shouldn't be comparing the age of the universe with a time calculated from a red shift between two objects in space.

It is not quite accurate to say the universe was 600m years old in this case.

Am I wrong? Can someone clarify for a nonscientist.

http://www.fromqu...niverse/ this article explains it well.
Torbjorn_Larsson_OM
4.3 / 5 (6) Aug 07, 2015
@enginarc: "we shouldn't be comparing the age of the universe with a time calculated from a red shift between two objects in space."

And we don't: "There are at least 3 ways that the age of the Universe can be estimated. I will describe

The age of the chemical elements.
The age of the oldest star clusters.
The age of the oldest white dwarf stars.

The age of the Universe can also be estimated from a cosmological model based on the Hubble constant and the densities of matter and dark energy."

http://www.astro....age.html

It is the model that - being careful with the phase transitions of the universe content which modifies adiabatic expansion rate - can be used to compare a cosmological redshift as a proxy for age estimates. (But usually astronomers use z directly, not even bothering to translate.)
Torbjorn_Larsson_OM
4.2 / 5 (5) Aug 07, 2015
I can add that I think, due to inflationary cosmology being known to such exquisite precision (< 0.2 % uncertainty of universe age, say), modern cosmology can derive trustfully z vs age estimates.

A decade ago, it was iffier. (Errors comparable to distance errors, i.e. 10s of % instead of fractions.)
mytwocts
5 / 5 (3) Aug 08, 2015
Good work, University of Leiden !
viko_mx
1 / 5 (2) Aug 12, 2015
"Not really. This galaxy was discovered 600 million years after the Big Bang. If anything, it's a discussion about the evolution of the Universe, not its formation."

Formation and evolution are two connected proceses. You can not separate them and to focus only ot one. Evulution of the universe is from the state with high order to the state with low order.

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