'Dropouts' pinpoint earliest galaxies

Nov 06, 2009
This is a composite of false color images of the galaxies found at the early epoch around 800 million years after the Big Bang. The upper left panel presents the galaxy confirmed in the 787 million year old universe. These galaxies are in the Subaru Deep Field. Credit: These images are created by M. Ouchi et al., which are the reproduction of Figure 3 in the Astrophysical Journal December 2009 issue.

Astronomers, conducting the broadest survey to date of galaxies from about 800 million years after the Big Bang, have found 22 early galaxies and confirmed the age of one by its characteristic hydrogen signature at 787 million years post Big Bang. The finding is the first age-confirmation of a so-called dropout galaxy at that distant time and pinpoints when an era called the reionization epoch likely began. The research will be published in a December issue of the Astrophysical Journal.

With recent technological advancements, such as the Wide-Field Camera 3 on the , there has been an explosion of research of the reionization period, the farthest back in time that astronomers can observe.

The Big Bang, 13.7 billion years ago, created a hot, murky universe. Some 400,000 years later, temperatures cooled, electrons and protons joined to form neutral , and the murk cleared. Some time before 1 billion years after the Big Bang, neutral hydrogen began to form stars in the first , which radiated energy and changed the hydrogen back to being ionized. Although not the thick plasma soup of the earlier period just after the Big Bang, this star formation started the reionization epoch. Astronomers know that this era ended about 1 billion years after the Big Bang, but when it began has eluded them and intrigued researchers like lead author Masami Ouchi of the Carnegie Observatories.

The U.S. and Japanese team led by Ouchi used a technique for finding these extremely distant galaxies. "We look for 'dropout' galaxies," explained Ouchi. "We use progressively redder filters that reveal increasing wavelengths of and watch which galaxies disappear from or 'dropout' of images made using those filters. Older, more distant galaxies 'dropout' of progressively redder filters and the specific wavelengths can tell us the galaxies' distance and age. What makes this study different is that we surveyed an area that is over 100 times larger than previous ones and, as a result, had a larger sample of early galaxies (22) than past surveys. Plus, we were able to confirm one galaxy's age," he continued. "Since all the galaxies were found using the same dropout technique, they are likely to be the same age."

Ouchi's team was able to conduct such a large survey because they used a custom-made, super-red filter and other unique technological advancements in red sensitivity on the wide-field camera of the 8.3-meter Subaru Telescope. They made their observations from 2006 to 2009 in the Subaru Deep Field and Great Observatories Origins Deep Survey North field. They then compared their observations with data gathered in other studies.

Astronomers have wondered whether the universe underwent reionization instantaneously or gradually over time, but more importantly, they have tried to isolate when the universe began reionization. Galaxy density and brightness measurements are key to calculating star-formation rates, which tell a lot about what happened when. The astronomers looked at star-formation rates and the rate at which hydrogen was ionized.

Using data from their study and others, they determined that the star-formation rates were dramatically lower from 800 millions years to about one billion years after the Big Bang, then thereafter. Accordingly, they calculated that the rate of ionization would be very slow during this early time, because of this low star-formation rate.

"We were really surprised that the rate of ionization seems so low, which would constitute a contradiction with the claim of NASA's WMAP satellite. It concluded that reionization started no later than 600 million years after the ," remarked Ouchi. "We think this riddle might be explained by more efficient ionizing photon production rates in early galaxies. The formation of massive stars may have been much more vigorous then than in today's galaxies. Fewer, massive stars produce more ionizing photons than many smaller stars," he explained.

Source: Carnegie Institution

Explore further: The changing laws that determine how dust affects the light that reaches us from the stars

add to favorites email to friend print save as pdf

Related Stories

Astronomers peer back to 'dawn of galaxies'

Oct 01, 2004

Detailed analysis of Hubble Space Telescope images has allowed astronomers to determine a major event in the evolution of the universe. The astronomers used the Hubble Space Telescope’s Ultra Deep Field (UDF) to peer 95 percent of the ...

When Dwarfs Gave Way to Giants

May 17, 2006

The first galaxies were small - about 10,000 times less massive than the Milky Way. Billions of years ago, those mini-furnaces forged a multitude of hot, massive stars. In the process, they sowed the seeds ...

Mysterious space blob discovered at cosmic dawn (w/Video)

Apr 22, 2009

(PhysOrg.com) -- A team of astronomers, led by Carnegie's Masami Ouchi, have discovered a mysterious, giant object that existed when the universe was only 800 million years old. Dubbed an extended "Lyman-Alpha ...

'Big baby' galaxy found in newborn Universe

Sep 28, 2005

The NASA/ESA Hubble Space Telescope and NASA’s Spitzer Space Telescope have teamed up to 'weigh' the stars in distant galaxies. One of these galaxies is not only one of the most distant ever seen, but it appears to be unusually ...

Stellar birth control in the early universe

Oct 01, 2006

An international team of astronomers based at Yale and Leiden University in The Netherlands found that "old stars" dominated many large galaxies in the early universe, raising the new question of why these ...

Recommended for you

ESO image: A study in scarlet

7 hours ago

This new image from ESO's La Silla Observatory in Chile reveals a cloud of hydrogen called Gum 41. In the middle of this little-known nebula, brilliant hot young stars are giving off energetic radiation that ...

Astronomers: 'Tilt-a-worlds' could harbor life

22 hours ago

A fluctuating tilt in a planet's orbit does not preclude the possibility of life, according to new research by astronomers at the University of Washington, Utah's Weber State University and NASA. In fact, ...

Pushy neighbors force stellar twins to diverge

Apr 15, 2014

(Phys.org) —Much like an environment influences people, so too do cosmic communities affect even giant dazzling stars: Peering deep into the Milky Way galaxy's center from a high-flying observatory, Cornell ...

Image: Multiple protostars within IRAS 20324+4057

Apr 14, 2014

(Phys.org) —A bright blue tadpole appears to swim through the inky blackness of space. Known as IRAS 20324+4057 but dubbed "the Tadpole", this clump of gas and dust has given birth to a bright protostar, ...

User comments : 15

Adjust slider to filter visible comments by rank

Display comments: newest first

Smurf
3 / 5 (2) Nov 06, 2009
So let me see, these galaxies formed in the 23 million years after neutral hydrogen began to form stars and created all the energy necessary for us to see it. Come on , cosmologists need to think this out.........
Question
2 / 5 (3) Nov 06, 2009
This big bang theory is running low on gas. It has had so many ad hoc patches added on over the years, to make it fit with the observed facts, that it is just not very believable any more. We need some competing alternative theories.
pauldentler
1 / 5 (3) Nov 06, 2009
This big bang theory is running low on gas. It has had so many ad hoc patches added on over the years, to make it fit with the observed facts, that it is just not very believable any more. We need some competing alternative theories.


Agreed, and here is precisely the problem with the gassy Big Bang, a massive galaxy supposedly 800 million years old, HUDF-JD2. It has the appearance of any galaxy that is billions of years older but shows up in a place galaxies that size are not supposed to be. The alternative hypothesis is the "orbiting universe", a universe where the movements of all bodies are in orbit about another larger body (including the galaxies), this would account for all galactic blue shift as well as galactic redshift.
vmircea
1 / 5 (1) Nov 07, 2009
What it see wmap satellite is others galaxy witch is at the limit of the observable universe, and another objects... Universe is infinte the limit is the limit of light that is coming from there.
frajo
3 / 5 (2) Nov 07, 2009
The alternative hypothesis is the "orbiting universe", a universe where the movements of all bodies are in orbit about another larger body

Isn't that the Ptolemaic epicycle model of ancient fame?
frajo
1.5 / 5 (2) Nov 07, 2009
What it see wmap satellite is others galaxy witch is at the limit of the observable universe, and another objects... Universe is infinte the limit is the limit of light that is coming from there.

You say these far-off well-developed galaxies are on the rim of the observable region of the universe and give us a glimpse into the non-observable part of the infinite universe?
Velanarris
5 / 5 (3) Nov 07, 2009
So let me see, these galaxies formed in the 23 million years after neutral hydrogen began to form stars and created all the energy necessary for us to see it. Come on , cosmologists need to think this out.........

You're completely ignoring spacial energy denisty, in addition to gravitic peturbation.

The big bang theory looks bunk until you understand all the intricate factors of it.
vmircea
not rated yet Nov 07, 2009

You say these far-off well-developed galaxies are on the rim of the observable region of the universe and give us a glimpse into the non-observable part of the infinite universe?

Yes the limit of what we see, the universe is eternal and infinit I'm shure of that, this part of universe is nothing compare to what is the universe realy is.
Shootist
not rated yet Nov 07, 2009
This big bang theory is running low on gas. It has had so many ad hoc patches added on over the years, to make it fit with the observed facts, that it is just not very believable any more. We need some competing alternative theories.


There are none.
frajo
3 / 5 (2) Nov 07, 2009
We need some competing alternative theories.


There are none.

Of course there are. One example:
http://wwwphy.pri...inh/npr/
pauldentler
1 / 5 (1) Nov 07, 2009
The alternative hypothesis is the "orbiting universe", a universe where the movements of all bodies are in orbit about another larger body

Isn't that the Ptolemaic epicycle model of ancient fame?

It is the law of "Conservation of Energy"
yyz
5 / 5 (2) Nov 08, 2009
Would that z=6.96 galaxy be IOK-1 ( http://arxiv.org/...9393.pdf )?

After parsing the press release and re-reading the paper I linked above, it appears this is indeed an extension of the work published in the 2006 paper. The current PI, Masami Ouchi, appears as a coauthor on the 2006 paper, which mentions in its summary that new more sensitive observations of the Subaru Deep Field would be conducted using newer red sensitive CCDs in the SuprimeCam on the 8.2m Subaru (not 8.3m as noted in Carnegie and Eurekalert press releases). In the 2006 paper, only two 'Lyman-alpha Emitters' were positively detected using the 'dropout' technique (IOK-1 & IOK-2), but only the former was detected spectroscopically. Now 22 LAEs have been detected in the Subaru Deep Field.

omatumr
1 / 5 (2) Nov 08, 2009
This big bang theory is running low on gas. It has had so many ad hoc patches added on over the years, to make it fit with the observed facts, that it is just not very believable any more. We need some competing alternative theories.


There are none.


Here's another http://tinyurl.com/ye337wo
Au-Pu
1 / 5 (1) Nov 15, 2009
My major complaint is with a choice of expression.
In paragraph 2 the writer said "Astronomers know.."
Sadly neither Astronomers or anyone else "knows".
At best they theorise.
And as so many respondents have said, "the big bang theory is running low on gas"
One thought that intrigues me is that the estimated period of time since the big bang is remarkably close to the limits of the visible universe, our visibility horizon
Perhaps all the missing matter is simply "out of sight".
frajo
3 / 5 (2) Nov 15, 2009
My major complaint is with a choice of expression.
In paragraph 2 the writer said "Astronomers know.."
Sadly neither Astronomers or anyone else "knows".
At best they theorise.

Whenever we communicate we rely on a lot of conventions. In astrophysical contexts conventionally the standard model is assumed. Only if you want to refer to non-standard theories you'll have to mention them.

Perhaps all the missing matter is simply "out of sight".
There are indeed theories which essentially tell us exactly this kind of thing.

More news stories

Let's put a sailboat on Titan

The large moons orbiting the gas giants in our solar system have been getting increasing attention in recent years. Titan, Saturn's largest moon, is the only natural satellite known to house a thick atmosphere. ...

ESO image: A study in scarlet

This new image from ESO's La Silla Observatory in Chile reveals a cloud of hydrogen called Gum 41. In the middle of this little-known nebula, brilliant hot young stars are giving off energetic radiation that ...

Progress in the fight against quantum dissipation

(Phys.org) —Scientists at Yale have confirmed a 50-year-old, previously untested theoretical prediction in physics and improved the energy storage time of a quantum switch by several orders of magnitude. ...