Massive galaxy had intense burst of star formation when universe was only 6 percent of current age

Apr 17, 2013 by Dave Finley
Background image is Herschel/SPIRE image of the portion of sky in which HFLS3 was found, with zoom. Upper-left inset is combined radio/millimeter/submillimeter image of the distant galaxy. Top right is VLA spectrum showing radio emission from Carbon Monoxide molecules. Credit: Riechers et al., ESA/Herschel/HerMES/IRAM/, NRAO/AUI/NSF.

(Phys.org) —Smaller begets bigger. Such is often the case for galaxies, at least: the first galaxies were small, then eventually merged together to form the behemoths we see in the present universe.

Those smaller galaxies produced stars at a modest rate; only later—when the universe was a couple of billion years old—did the vast majority of larger galaxies begin to form and accumulate enough gas and dust to become prolific star factories. Indeed, astronomers have observed that these star factories—called starburst galaxies—became prevalent a couple of billion years after the Big Bang.

But now a team of astronomers, which includes several from the California Institute of Technology (Caltech), has discovered a dust-filled, massive galaxy churning out stars when the cosmos was a mere 880 million years old—making it the earliest starburst galaxy ever observed.

The galaxy is about as massive as our Milky Way, but produces stars at a rate 2,000 times greater, which is a rate as high as any galaxy in the universe. Generating the mass equivalent of 2,900 suns per year, the galaxy is especially prodigious—prompting the team to call it a "maximum-starburst" galaxy.

"Massive, intense starburst galaxies are expected to only appear at later cosmic times," says Dominik Riechers, who led the research while a senior research fellow at Caltech. "Yet, we have discovered this colossal starburst just 880 million years after the Big Bang, when the universe was at little more than 6 percent of its current age." Now an assistant professor at Cornell, Riechers is the first author of the paper describing the findings in the April 18 issue of the journal Nature.

While the discovery of this single galaxy isn't enough to overturn current theories of galaxy formation, finding more galaxies like this one could challenge those theories, the astronomers say. At the very least, theories will have to be modified to explain how this galaxy, dubbed HFLS3, formed, Riechers says.

"This galaxy is just one spectacular example, but it's telling us that extremely vigorous star formation was possible early in the universe," says Jamie Bock, professor of physics at Caltech and a coauthor of the paper.

The astronomers found HFLS3 chock full of molecules such as carbon monoxide, ammonia, hydroxide, and even water. Because most of the elements in the universe—other than hydrogen and helium—are fused in the nuclear furnaces of stars, such a rich and diverse chemical composition is indicative of active star formation. And indeed, Bock says, the chemical composition of HFLS3 is similar to those of other known starburst galaxies that existed later in cosmic history.

Last month, a Caltech-led team of astronomers—a few of whom are also authors on this newer work—discovered dozens of similar galaxies that were producing stars as early as 1.5 billion years after the Big Bang. But none of them existed as early as HFLS3, which has been studied in much greater detail.

Those previous observations were made possible by gravitational lensing, in which large foreground galaxies act as cosmic magnifying glasses, bending the light of the starburst galaxies and making their detection easier. HFLS3, however, is only weakly lensed, if at all. The fact that it was detectable without the help of lensing means that it is intrinsically a bright galaxy in far-infrared light—nearly 30 trillion times as luminous as the sun and 2,000 times more luminous than the Milky Way.

Because the galaxy is enshrouded in dust, it's very faint in visible light. The galaxy's stars, however, heat up the dust, causing it to radiate in infrared wavelengths. The astronomers were able to find HFLS3 as they sifted through data taken by the European Space Agency's Herschel Space Observatory, which studies the infrared universe. The data was part of the Herschel Multi-tiered Extragalactic Survey (HerMES), an effort co-coordinated by Bock to observe a large patch of the sky (roughly 1,300 times the size of the moon) with Herschel.

Amid the thousands of galaxies detected in the survey, HFLS3 appeared as just a faint dot—but a particularly red one. That caught the attention of Darren Dowell, a visiting associate at Caltech who was analyzing the HerMES data. The object's redness meant that its light was being substantially stretched toward longer (and redder) wavelengths by the expansion of the universe. The more distant an object, the more its light is stretched, and so a very red source would be very far away. The only other possibility would be that—because cooler objects emit light at longer wavelengths—the object might be unusually cold; the astronomers' analysis, however, ruled out that possibility. Because it takes the light billions of years to travel across space, seeing such a distant object is equivalent to looking deep into the past. "We were hoping to find a massive starburst galaxy at vast distances, but we did not expect that one would even exist that early in the universe," Riechers says.

To study HFLS3 further, the astronomers zoomed in with several other telescopes. Using the Combined Array for Research in Millimeter-Wave Astronomy (CARMA)—a series of telescope dishes that Caltech helps operate in the Inyo Mountains of California—as well as the Z-Spec instrument on the Caltech Submillimeter Observatory on Mauna Kea in Hawaii, the team was able to study the chemical composition of the galaxy in detail—in particular, the presence of water and carbon monoxide—and measure its distance. The researchers also used the 10-meter telescope at the W. M. Keck Observatory on Mauna Kea to determine to what extent HFLS3 was gravitationally lensed.

This galaxy is the first such object in the HerMES survey to be analyzed in detail. This type of galaxy is rare, the astronomers say, but to determine just how rare, they will pursue more follow-up studies to see if they can find more of them lurking in the HerMES data. These results also hint at what may soon be discovered with larger infrared observatories, such as the new Atacama Large Millimeter/submillimeter Array (ALMA) in Chile and the planned Cerro Chajnantor Atacama Telescope (CCAT), of which Caltech is a partner institution.

The title of the Nature paper is "A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34." In addition to Riechers, Bock, and Dowell, the other Caltech authors of the paper are visiting associates in physics Matt Bradford, Asantha Cooray, and Hien Nguyen; postdoctoral scholars Carrie Bridge, Attila Kovacs, Joaquin Vieira, Marco Viero, and Michael Zemcov; staff research scientist Eric Murphy; and Jonas Zmuidzinas, the Merle Kingsley Professor of Physics and the Chief Technologist at NASA's Jet Propulsion Laboratory (JPL). There are a total of 64 authors. Bock, Dowell, and Nguyen helped build the Spectral and Photometric Imaging Receiver (SPIRE) instrument on Herschel.

Explore further: Millisecond pulsars clearly demonstrate that pulsars are neutron stars

More information: Paper dx.doi.org/10.1038/nature12050

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theon
1 / 5 (4) Apr 17, 2013
Don't give away the redshift, that's for wise men, this release is for the plain people.
rwinners
1 / 5 (3) Apr 17, 2013
Hypothesis upon another.
LarryD
5 / 5 (3) Apr 17, 2013
Don't give away the redshift, that's for wise men, this release is for the plain people.

Hey theon, I resent that. I'm a layman...er what are 'plain people'?...but I'm extremely interested in these topics.
Surely as our technology becomes more sophisticated we will find more anomalies. Is there any particular reason why I shouldn't trust this Caltech research?
ROBTHEGOB
1 / 5 (2) Apr 18, 2013
The Universe has no age. There was no Big Bang. The world is not flat. Get over it.
rwinners
1 / 5 (1) Apr 18, 2013
The Universe has no age. There was no Big Bang. The world is not flat. Get over it.


Actually, all said ages are 'theoretical'. No scientist states the age or size of the universe as factual.
theon
1 / 5 (1) Apr 18, 2013
Don't give away the redshift, that's for wise men, this release is for the plain people.

Hey theon, I resent that. I'm a layman...er what are 'plain people'?...but I'm extremely interested in these topics.
Surely as our technology becomes more sophisticated we will find more anomalies. Is there any particular reason why I shouldn't trust this Caltech research?


It was meant to be cynical. I always regret that they don't give this simple number, age and redshift together.
Eoprime
1 / 5 (1) Apr 18, 2013

"The title of the Nature paper is "A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34.""

First read, then post.
Fleetfoot
3.7 / 5 (6) Apr 18, 2013
I presume, everyone realize, we are just one step forward toward the infinite random universe model of AWT.


No, everyone realises there is no such thing as AWT, it is just your random and baseless posts.

(Caltech), has discovered a dust-filled, massive galaxy churning out stars when the cosmos was a mere 880 million years old—making it the earliest starburst galaxy ever observed. The galaxy is about as massive as our Milky Way, but produces stars at a rate 2,000 times greater


That is what is expected in the BB model, with hydrogen getting used up rapidly in the early universe. The first galaxy the size of the Milky way are predicted to appear around 400 million years so this is well into the correct period. The rate is high for formation theories that say the light from the star formation should push the gas away and tend to quench the process but that's detail that we are still learning.
Q-Star
3 / 5 (6) Apr 18, 2013
That is what is expected in the BB model, with hydrogen getting used up rapidly in the early universe
versus
Massive, intense starburst galaxies are expected to only appear at later cosmic times" says Dominik Riechers, who led the research at Caltech
You should tell the Dominik, he doesn't understand his stuff...


Zephyr, it is ya who doesn't understand Riechers' stuff. Do ya realize how very rare this sort of object is? It would like finding a human who stood 3 meters tall, and saying that disproves what most anthropologists call "normal" or "average", 1.75 meters.

Context and perspective are more important than "your" intuition.
Fleetfoot
4 / 5 (4) Apr 18, 2013
That is what is expected in the BB model, with hydrogen getting used up rapidly in the early universe
versus
Massive, intense starburst galaxies are expected to only appear at later cosmic times" says Dominik Riechers, who led the research at Caltech
You should tell the Dominik, he doesn't understand his stuff...


Your confusion is that there is a difference between a massive galaxy and a starburst galaxy. This question came up some weeks ago because there is an error in the WMAP graphic:

http://map.gsfc.n...ne75.jpg

It shows "1st Stars about 400 million yrs" when they obviously must have existed prior to the end of the dark ages. The first stars are expected to be no later than z=25 or about 130 million years while 400 million is the expected time of the first large galaxies.

I personally checked this with Prof Djorgovski, also of Caltech:

http://www.astro....ski.html
Fleetfoot
4 / 5 (4) Apr 18, 2013
The first stars are expected to be no later than z=25 or about 130 million years while 400 million is the expected time of the first large galaxies.


See also slide 20 of this from Berkeley:

http://astro.berk...8-08.pdf

The Naoz paper is here:

http://intl-mnras...L98.full

This one from Fialkov finds a similar result:

http://arxiv.org/abs/1110.2111

Both suggest the first stars could have been as early z=65 or just 30 million years but that is beyond even JWST so it may be a long time until we can tell.

Anyway, the first large galaxies are expected to have appeared well before 800 million years, it is the starburst that is unusual. In comparison, our galaxy only produces about 6 new stars per year.
ValeriaT
1 / 5 (1) Apr 18, 2013
What I'm is missing is the scientific, i.e. critical judging of existing theories. In Big Bang theory the matter got very finely dispersed with inflation. It's concentration was much lower than sparse clouds around most of galaxies and it condensed gradually. Under normal circumstances the stars should never form there.
Q-Star
3 / 5 (6) Apr 18, 2013
What I'm is missing is the scientific, i.e. critical judging of existing theories.


We've been telling ya that for years now Zeph.

In Big Bang theory the matter got very finely dispersed with inflation.


Uh, correct, I think, but I have trouble at times understanding exactly what ya are saying. My fault, not yours.

It's concentration was much lower than sparse clouds around most of galaxies and it condensed gradually.


That's where ya're confusing things, Zeph,,, the "much lower" part,,,

The "condensed gradually" part is subjective. How much time is gradually? Condensed from what density?

Everything reported in this article fits quite nicely with the so-called "Big Bang" model of the early universe. It's all about context and perspective. Early universe cosmology is not an exact science, like say, nuclear physics or organic chemistry.
Fleetfoot
3.7 / 5 (3) Apr 18, 2013
What I'm is missing is the scientific ...


Science is based on observations such as this.

In Big Bang theory the matter got very finely dispersed with inflation.


No, matter was produced after the end of inflation. The energy is thought to have come from the collapse of the field that caused inflation. Baryogenesis and nucleogenesis were much later.

It's concentration was much lower than sparse clouds around most of galaxies


Dark matter was able to start condensing around the time of nucleogenesis so the density was far higher, around the same as Earth's stratosphere from memory.

and it condensed gradually.


Yes.

Under normal circumstances the stars should never form there.


True, but dark matter isn't normal matter. It started forming clumps earlier and the baryonic matter fell into those potential wells when it decoupled from radiation and the CMBR was released. When you take that into account, the time required works out just right.