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“Pristine” gas from birth of universe detected

Oct. 3, 2013
Courtesy of the W.M. Keck Observatory
and World Science staff

As­tro­no­mers say they have de­tected streams of “pris­tine” hy­dro­gen gas left over di­rectly from the birth of the uni­verse.

The cold gas is flow­ing, they said, in­to a gal­axy that is now seen as it looked about 11 bil­lion years ago, due to the time its light takes to get he­re.

A com­bi­na­tion of a su­per­com­puter vis­u­al­i­za­tion and art­ist’s il­lus­tra­tion. It shows a gal­axy (cen­ter) with in­com­ing cold gas flow, pro­duced by ren­der­ing the gas dis­tri­bu­tion in a su­per­com­puter sim­u­la­tion of a form­ing gal­axy. A stream of pri­mor­di­al in­flow­ing gas is il­lu­mi­nat­e from be­hind by a dis­tant back­ground qua­sar (low­er left; qua­sar added by an art­ist, along with the star­ry back­ground). The sim­u­la­tion was run by the Mak­ing Ga­lax­ies in a Cos­mo­lo­g­i­cal Con­text (MaG­ICC) proj­ect in the the­o­ry group at the Max Planck In­sti­tute for As­tron­o­my.


Pro­fuse gas flows like this are thought to be key to ex­plain­ing that early era, when ga­lax­ies were co­pi­ously form­ing stars from the gas. A si­m­i­lar flow could have con­tri­but­ed to the crea­t­ion of our own gal­axy.

The as­tro­no­mers – led by Neil Crigh­ton of Swin­burne Uni­vers­ity in the U.K. – pub­lished the find­ings Oct. 2 in the re­search jour­nal As­t­ro­phys­i­cal Jour­nal Let­ters.

The dis­tant hy­dro­gen usu­ally can’t be de­tected. But in this case it was, thanks to a co­in­ci­den­tal light­ing ar­range­ment pro­vid­ed by a dis­tant, ex­tremely bright ob­ject known as a qua­sar, ac­cord­ing to Crigh­ton’s group. 

The find­ings came from a sys­tem­at­ic sur­vey us­ing the Large Bin­oc­u­lar Tel­e­scope on Mount Gra­ham, Ar­i­zo­na and an in­stru­ment called a spec­tro­graph on the Keck I tel­e­scope on the sum­mit of Mauna Kea, Ha­waii. 

Cos­mol­o­gists be­lieve early ga­lax­ies re­ceived their ma­te­ri­al from a vast res­er­voir of pris­tine hy­dro­gen float­ing be­tween ga­lax­ies. About 10 bil­lion years ago when the uni­verse was one-fifth its cur­rent age, stud­ies have found, fledg­ling ga­lax­ies were form­ing new stars at nearly 100 times their cur­rent rate. This ac­ti­vity would re­quire some fu­el in the form of gas, since that is what makes up stars.

In the past dec­ade, su­per­com­puter sim­ula­t­ions of gal­axy forma­t­ion have pre­dicted that this gas fun­nels in­to ga­lax­ies along thin “cold streams” which, like streams of snow melt feed­ing a moun­tain lake, chan­nel cool gas from the sur­round­ing area on­to ga­lax­ies.

Test­ing these pre­dic­tions is­n’t easy, as such gas at the edges of ga­lax­ies is very dark. In­stead, the team of as­tro­no­mers searched for places where qua­sars could pro­vide help­ful light. Quasars are ga­lax­ies that briefly shine as the bright­est ob­jects in the uni­verse as their cen­tral ob­ject, a black hole, sucks up ma­te­ri­al in a vi­o­lent pro­cess. If a cloud of gas is float­ing somewhere be­tween that qua­sar and our tel­e­scopes, the gas is seen to ab­sorb the qua­sar’s light at very spe­cif­ic fre­quen­cies, or “col­ors.” The light reaches us with those fre­quen­cies blacked out. The pat­tern of mis­sing fre­quen­cies re­veals the make­up, thick­ness and tempe­rature of the gas.

Crighton and col­leagues used this meth­od to make their de­ter­mina­t­ions about the gal­axy, de­not­ed Q1442-MD50. Key to their find­ing was that the mis­sing fre­quen­cies re­vealed the pres­ence of deu­ter­i­um, a spe­cial va­riant, or iso­tope, of hy­dro­gen. Cal­cula­tions indi­cate that deu­ter­i­um was cre­at­ed just min­utes af­ter the “Big Bang,” an explosion-like event thought to have giv­en birth to the uni­verse.

Deu­ter­i­um is de­stroyed over time as the gas cy­cles in and out of stars, so the pres­ence of deu­ter­i­um sig­nals “pris­tine” gas nev­er be­fore used to form stars, the as­tro­no­mers said.

“This is not the first time as­tro­no­mers have found a gal­axy with near­by gas, re­vealed by a qua­sar. But it is the first time that ever­ything fits to­geth­er,” Crigh­ton said. “The gal­axy is vig­or­ously form­ing stars, and the gas prop­er­ties clearly show that this is pris­tine ma­te­ri­al, left over from the early uni­verse shortly af­ter the Big Bang.”

The as­tro­no­mers want to find about 10 more ex­am­ples of si­m­i­lar gas flows in or­der to com­pare them against sim­ula­t­ions of gal­axy forma­t­ion and test them for ac­cu­ra­cy. The work so far sug­gest the flows are quite com­mon, they added.

“We only had to search 12 qua­sar-gal­axy pairs to disco­ver this ex­am­ple. This rate is in rough agree­ment with the pre­dic­tions of su­per­com­puter sim­ula­t­ions,” said Jo­seph Hen­nawi, lead­er of a re­search group called ENIG­MA at the Max Planck In­sti­tute for As­tronomy in Ger­ma­ny. That pro­vides a “vote of con­fi­dence for our cur­rent the­o­ries of how ga­lax­ies formed,” added Hen­nawi, who is co­or­di­nat­ing the sur­vey of qua­sar-gal­axy pairs that led to the new find­ings.


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Astronomers say they have detected streams of “pristine” hydrogen gas left over directly from the birth of the universe. The cold gas is flowing, they said, into a galaxy that is now seen as it looked about 11 billion years ago, due to the time its light takes to get here. Profuse gas flows like this are thought to be key to explaining that early era, when galaxies were copiously forming stars from the gas. A similar flow could have contributed to the creation of our own galaxy. The astronomers – led by Neil Crighton of Swinburne University in the U.K. – published the findings Oct. 2 in the Astrophysical Journal Letters. The distant hydrogen usually can’t be detected. But in this case it was, thanks to a coincidental lighting arrangement provided by a distant, extremely bright object known as a quasar, according to Crighton’s group. The findings came from a systematic survey with using the Large Binocular Telescope on Mount Graham, Arizona and an instrument called a spectrograph on the 10 meter Keck I telescope on the summit of Mauna Kea, Hawaii. Cosmologists believe early galaxies received their material from a vast reservoir of pristine hydrogen floating between galaxies. About 10 billion years ago when the Universe was one-fifth its current age, studies have found, fledgling galaxies were forming new stars at nearly 100 times their current rate. This activity would require some fuel in the form of gas, since that is what makes up stars. In the past decade, supercomputer simulations of galaxy formation have predicted that this gas funnels into galaxies along thin “cold streams” which, like streams of snow melt feeding a mountain lake, channel cool gas from the surrounding intergalactic medium onto galaxies. Testing these predictions isn’t easy, as such gas at the edges of galaxies is very dark. Instead, the team of astronomers searched for places where quasars could provide helpful light. Quasars are galaxies that briefly shine as the brightest objects in the universe as their central object, a black hole, sucks up material in a violent process. If a cloud of gas is floating somewhere between that quasar and our telescopes, the gas absorbs the quasar’s light at very specific frequencies, or “colors.” The light reaches us with those frequencies blacked out. The pattern of missing frequencies reveals the makeup, thickness and temperature of the gas. Crighton and colleagues used this method to make their determinations about the galaxy, denoted Q1442-MD50. Key to their finding was that the missing frequencies revealed the presence of deuterium, a special form hydrogen created just minutes after the “Big Bang,” an explosion-like event thought to have given birth to the universe. Deuterium is destroyed over time as the gas cycles in and out of stars, so the presence of deuterium signals “pristine” gas never before used to form stars, the astronomers said. “This is not the first time astronomers have found a galaxy with nearby gas, revealed by a quasar. But it is the first time that everything fits together,” Crighton said. “The galaxy is vigorously forming stars, and the gas properties clearly show that this is pristine material, left over from the early universe shortly after the Big Bang.” The astronomers want to find about 10 more examples of similar gas flows in order to compare them against simulations of galaxy formation and test them for accuracy. The work so far suggest the flows are quite common, they added. “We only had to search 12 quasar-galaxy pairs to discover this example. This rate is in rough agreement with the predictions of supercomputer simulations,” said Joseph Hennawi, leader of the research group called ENIGMA at the Max Planck Institute for Astronomy in Germany. That provides a “vote of confidence for our current theories of how galaxies formed,” added Hennawi, who is coordinating the survey of quasar-galaxy pairs that led to the new findings.