. Medical and Hospital News .




.
TIME AND SPACE
Discovery of the Most Distant Galaxy in the Cosmic Dawn
by Staff Writers
Tokyo, Japan (SPX) Jun 11, 2012

Cosmic history from the Big Bang to the present. (Credit: NAOJ). For a larger version of this image please go here.

A team of astronomers led by Takatoshi Shibuya (The Graduate University for Advanced Studies, Japan), Dr. Nobunari Kashikawa (National Astronomical Observatory of Japan), Dr. Kazuaki Ota (Kyoto University), and Dr. Masanori Iye (National Astronomical Observatory of Japan) has used the Subaru and Keck Telescopes to discover the most distant galaxy ever found, SXDF-NB1006-2, at a distance of 12.91 billion light years from the Earth.

This galaxy is slightly farther away than GN-108036, which Subaru Telescope discovered last year and was the most distant galaxy discovered at the time (Note 1). In addition, the team's research verified that the proportion of neutral hydrogen gas in the 750-million-year-old early Universe was higher than it is today.

These findings help us to understand the nature of the early Universe during the "cosmic dawn", when the light of ancient celestial objects and structures appeared from obscurity.

Astronomers think that the our Universe began 13.7 billion years ago at the Big Bang. The exteme temperature and density of this fireball decreased rapidly as its volume increased. Hot cosmic plasma composed mainly of protons and electrons recombined to form neutral hydrogen atoms within 380,000 years after the Big Bang; this was the beginning of the cosmic "dark age."

From then on, the gas continued to cool and fluctuated in density. About 200 to 500 million years after the Big Bang, the dense parts of neutral hydrogen clouds contracted under their own gravity, and the first stars and galaxies formed. The radiation from this first generation of stars started to heat and reionize the hydrogen in nearby space, eventually leading to the reionization of the entire Universe.

This was the era of "cosmic reionization" (Figure 1) or the "cosmic dawn". The current team focused their research on identifying the exact epoch of the cosmic dawn in an effort to answer major astronomical questions about the history of our Universe.

How did the team design research to explore such an ancient, extremely distant time? Their first steps were to conduct a survey of distant galaxies and measure their number and brightness. Because light from the distant Universe takes time to reach the Earth, identification of more distant galaxies allows astronomers to trace farther back in time and locate the epoch of the cosmic dawn.

However, neutral hydrogen in intergalactic space dimmed the light from galaxies before the cosmic dawn and made them more difficult to observe. Because the team needed to search a vast area for objects in the far distant Universe (Note 2), they used the prime focus camera mounted on the Subaru Telescope (Suprime-Cam) for their initial surveys.

Suprime-Cam captures images of objects in a wide field of view from the large, 8.2 m primary mirror of the Subaru Telescope and is well-known for discovering faint, far distant galaxies and then measuring the amount of neutral hydrogen in the early Universe (Note 3).

The use of Suprime-Cam was even more compelling with the 2008 installation of new detectors with a sensitivity about twice as high as their predecessors, particularly in the red wavelengths (Note 4).

Armed with the most sensitive eyes in the world, the researchers could carry out surveys for extremely distant galaxies (beyond redshift 7, where the majority of energy output from galaxies is detected in red wavelengths). To fine-tune their survey even more, a team led by Dr. Iye constructed a new special filter named NB1006 through which they could selectively identify the light of distant galaxies at a redshift of nearly 7.3.

The team used Suprime-Cam, complete with its new, highly sensitive detectors, attached the NB1006 filter to observe two specifically designated regions of the sky for detailed study: the Subaru Deep Field and the Subaru XMM-Newton Deep Survey Field.

After a total of 37 hours in 7 nights of observations in these wide fields, the team carefully processed the images they had obtained. Shibuya measured the color of 58,733 objects in the images and identified four galaxy candidates at a redshift of 7.3. A careful investigation of the brightness variation of the objects allowed the team to narrow down the number of candidates to two.

Then it was necessary for the team to make spectroscopic observations to confirm the nature of these candidates. They observed the two galaxy candidates with two spectrographs, the Faint Object Camera and Spectrograph (FOCAS) on the Subaru Telescope and the Deep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck Telescope, and identified one candidate for which a characteristic emission line of distant galaxies could be detected.

The current team found that the proportion of neutral hydrogen was increasing in the far distant Universe. They concluded that about 80 percent of the hydrogen gas in the ancient Universe, 12.91 billion years ago at a redshift of 7.2, was neutral.

In sum, this careful research plan and procedures, including the appropriate removal of contaminations that could lead to false results, resulted in the successful discovery and confirmation of the most distant galaxy ever discovered: SXDF-NB1006-2 (Figures 2 and 3). In addition, the findings gave the team confidence that they were observing an object during the last phase of the cosmic dawn.

Although finding just one galaxy at a critical epoch is exciting by itself, it is not a sufficient sample to characterize the entire epoch. Precise measurement of the number of galaxies during the cosmic dawn requires surveys of even wider fields.

The scheduled 2012 installation of Subaru's new instrument, Hyper Suprime-Cam (HSC) will allow researchers to observe a field of view seven times greater than that of Suprime-Cam and opens the door to a huge galaxy sample beyond redshift 7. Observations with HSC are steps in the direction of uncovering the dark periods of the Universe and understanding the physical properties and formation of the first stars and galaxies.

Shibuya summarized the team's future intent and hopes: "By conducting an extremely wide HSC survey for distant galaxies beyond redshift seven, we will find the mechanisms of the cosmic reionization in a variety of ways, not just by investigating their number and brightness."

Dr. Iye, the leader of the Thirty Meter Telescope (TMT) project at the National Astronomical Observatory of Japan (NAOJ), added, "We have been pushing the limits of 8-10 m class telescopes to detect distant galaxies. The 30 m mirror of the TMT will be able to gather up to ten times more light than current large telescopes and detect faint light from galaxies up to a redshift of 14. The day is not so far off when the mysteries of the dark ages of the Universe and the physical properties of the first galaxies will be revealed."

These results will be published in the June 20, 2012, edition of the Astrophysical Journal. This research was supported by The Japan Society for the Promotion of Science through Grant-in-Aid for Scientific Research 23340050 and 19104004.

Related Links
Subaru Telescope
Understanding Time and Space




.
.
Get Our Free Newsletters Via Email
...
Buy Advertising Editorial Enquiries




.

. Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle



TIME AND SPACE
The Older We Get, The Less We Know Cosmologically
Cambridge MA (SPX) May 25, 2012
The universe is a marvelously complex place, filled with galaxies and larger-scale structures that have evolved over its 13.7-billion-year history. Those began as small perturbations of matter that grew over time, like ripples in a pond, as the universe expanded. By observing the large-scale cosmic wrinkles now, we can learn about the initial conditions of the universe. But is now really t ... read more


TIME AND SPACE
Study predicts imminent irreversible planetary collapse

Japan agency sorry for comparing radiation to wife

Lithuania launches regional nuclear safety watchdog

Italy's quake-struck north tries to reassure tourists

TIME AND SPACE
Apple fends off Android challenge with maps, Siri

Boeing, Raytheon and Harris to Pursue GPS Control Segment Sustainment Contract

Revamped Google maps goes offline for mobile

USAF Awards Lockheed Martin GPS III Flight Operations Contract

TIME AND SPACE
How infectious disease may have shaped human origins

Homo heidelbergensis was only slightly taller than the Neanderthal

Fossil discovery sheds new light on evolutionary history of higher primates

Monkey lip smacks provide new insights into the evolution of human speech

TIME AND SPACE
Ecologists Call for Preservation of Planet's Remaining Biological Diversity

Many questions as Rio Summit seeks to help sick planet

Wales seeking Rio+20 sustainability impact

Scientists uncover evidence of impending tipping point for Earth

TIME AND SPACE
Mama Portia dishes out help for AIDS orphans

Revealed: Secret of HIV's natural born killers

New study shows why swine flu virus develops drug resistance

China faces 'serious' epidemic of drug-resistant TB

TIME AND SPACE
Hong Kong official questions China dissident death

'Long Hair' Leung: Hong Kong's rebel with a cause

Hundreds march in Hong Kong over dissident's death

Top China dissident found dead

TIME AND SPACE
Incidence, types of marine piracy studied

Iran navy saves US freighter from pirates: report

Jailing of marines hitting anti-piracy efforts: Italy

Armed N.Koreans kidnap Chinese sailors: reports

TIME AND SPACE
Walker's World: The euro's unknowns

Outside View: EU bailout is no cure

Expectations for the Rio Summit, in quotes

China revives key economic reform amid transition


Memory Foam Mattress Review

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

.

The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement