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Giant black holes from chaotic early era coming to light

Oct. 9, 2012
Courtesy of the Royal Astronomical Society
and World Science staff

Cutting-edge sky sur­veys have re­vealed a pre­vi­ously un­seen group of gi­ant, fast-grow­ing black holes from a vi­o­lent early pe­ri­od in cos­mic his­to­ry, as­tro­no­mers say.

Re­search­ers claim the find­ings could have spe­cial sig­nif­i­cance be­cause they shed light on how huge black holes and ga­lax­ies shaped each oth­er’s early de­vel­op­ment.

Astronomers say the red dot is an image of the galaxy ULASJ1234+0907, 11 billion light years from Earth. Dust obscures the object in the visible light, so this image was taken using data from infrared light surveys (Credit: the UKIDSS and the Wide-field Infrared Survey Explorer observatory)
A black hole is an ob­ject so com­pact that its gravita­t­ional force be­comes all-pow­er­ful in its re­gion of space, and thus dra­gs in an­y­thing that gets too close, in­clud­ing light. 

Gi­ant, or “su­per­mas­sive,” black holes are be­lieved to sit at the cen­ters of ga­lax­ies, in­clud­ing our own.

The black holes de­scribed in the new re­search were pre­vi­ously un­de­tected be­cause thick lay­ers of dust en­shroud them. But they turn out to have been re­leas­ing co­pi­ous radia­t­ion through vi­o­lent in­ter­ac­tions with their host ga­lax­ies, ac­cord­ing to the au­thors of the new re­search. 

Their re­port on the find­ings is to ap­pear in the jour­nal Monthly No­tices of the Roy­al As­tro­nom­i­cal So­ci­e­ty and is on­line here.

The most ex­treme ob­ject in the study is a su­per­mas­sive black hole called ULASJ1234+0907. This ob­ject, lo­cat­ed in the di­rec­tion of the con­stella­t­ion of Vir­go, is so far away that the light from it has tak­en 11 bil­lion years to reach us, so we see it as it ap­peared in the early uni­verse. The mon­ster black hole is es­ti­mated to have more than 10 bil­lion times the mass (weight) of the Sun and 10,000 times the mass of the su­per­mas­sive black hole in our own Milky Way, mak­ing it one of the big­gest black holes known.

But the re­search in­di­cates there may be as many as 400 such gi­ant black holes in the part of the uni­verse that we can ob­serve. 

“These re­sults could have a sig­nif­i­cant im­pact on stud­ies of su­per­mas­sive black holes,” said Manda Banerji of the Uni­vers­ity of Cam­bridge, lead au­thor of the pa­per. “Most black holes of this kind are seen through the mat­ter they dra­g in. As the neigh­bour­ing ma­te­ri­al spi­rals in to­wards the black holes, it heats up. As­tro­no­mers are able to see this radia­t­ion and ob­serve these sys­tems. Al­though these black holes have been stud­ied for some time, the new re­sults in­di­cate that some of the most mas­sive ones may have so far been hid­den from our view.” 

The new­found black holes, de­vour­ing the equiv­a­lent of sev­er­al hun­dred Suns eve­ry year, are ex­pected to shed light on the pro­cesses gov­ern­ing all su­per­mas­sive black hole growth. By de­sign, the sam­pled black holes come from a pe­ri­od “cor­re­spond­ing to the peak of star forma­t­ion and black-hole” growth in our roughly 13.7-bil­lion-year-old uni­verse, the sci­en­tists wrote.

The most mas­sive ga­lax­ies and their cen­tral black holes are widely be­lieved to have grown through vi­o­lent col­li­sions with oth­er ga­lax­ies, which trig­ger the forma­t­ion of stars and pro­vides food for the black holes to de­vour. These vi­o­lent col­li­sions would al­so have pro­duced abun­dant dust, which briefly en­shrouds the gorg­ing black hole.

The most spec­tac­u­lar ex­am­ple al­ready known of a dusty, grow­ing black hole in the rel­a­tively near­by uni­verse is the well-stud­ied gal­axy Markar­ian 231 lo­cat­ed at a much smaller dis­tance of 600 mil­lion light-years away, Banerji and col­leagues said. A light-year is the dis­tance light trav­els in a year. Stud­ies with the Hub­ble Space Tel­e­scope in­di­cate Markar­ian 231 crashed in­to anoth­er gal­axy fairly re­cently in cos­mic his­to­ry. 

ULASJ1234+0907 is be­ing de­scribed as a more ex­treme ver­sion of this near­by gal­axy, in­di­cat­ing con­di­tions in the early cosmos were much more tur­bu­lent and inhospita­ble than to­day.

The Cam­bridge re­search­ers used in­fra­red-light sur­veys be­ing car­ried out on the U.K. In­fra­red Tel­e­scope to peer through the dust and lo­cate the gi­ant black holes for the first time. In­fared light is a low-energy form of light not vis­i­ble to the un­aided eye. “These re­sults are par­tic­u­larly ex­cit­ing be­cause they show that our new in­fra­red sur­veys are find­ing su­per mas­sive black holes that are invis­i­ble in op­ti­cal sur­veys. These new quasars are im­por­tant be­cause we may be catch­ing them as they are be­ing fed through col­li­sions with oth­er ga­lax­ies,” said Rich­ard Mc­Mah­on at Cam­bridge, co-au­thor of the stu­dy.

He added that ob­serva­t­ions with the new At­a­cama Large Mil­li­me­ter Ar­ray tel­e­scope in Chil­e “will al­low us to di­rectly test this pic­ture by de­tect­ing the mi­cro­wave-fre­quen­cy radia­t­ion emit­ted by the vast amounts of gas in the col­lid­ing ga­lax­ies.”

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Cutting-edge sky surveys using infrared light have revealed a previously unseen group of giant, fast-growing black holes from a violent early period in cosmic history, astronomers say. Researchers claim the findings could have special significance because they shed light on how huge black holes and galaxies shaped each other’s early development. A black hole is an object so compact that its gravitational force becomes all-powerful in its region of space, and thus drags in anything that gets too close, including light. Giant, or “supermassive,” black holes are believed to sit at the centres of galaxies, including our own. The black holes described in the new research were previously undetected because thick layers of dust enshroud them. But they turn out to have been releasing copious radiation through violent interactions with their host galaxies, according to the authors of the new research. Their report is to appear in the journal Monthly Notices of the Royal Astronomical Society and is online here. The most extreme object in the study is a supermassive black hole called ULASJ1234+0907. This object, located in the direction of the constellation of Virgo, is so far away that the light from it has taken 11 billion years to reach us, so we see it as it appeared in the early universe. The monster black hole has more than 10 billion times the mass of the Sun and 10,000 times the mass of the supermassive black hole in our own Milky Way, making it one of the biggest black holes known. But the research indicates there may be as many as 400 such giant black holes in the part of the universe that we can observe. “These results could have a significant impact on studies of supermassive black holes,” said Manda Banerji of the University of Cambridge, lead author of the paper. “Most black holes of this kind are seen through the matter they drag in. As the neighbouring material spirals in towards the black holes, it heats up. Astronomers are able to see this radiation and observe these systems. Although these black holes have been studied for some time, the new results indicate that some of the most massive ones may have so far been hidden from our view.” The newfound black holes, devouring the equivalent of several hundred Suns every year, are expected to shed light on the processes governing all supermassive black hole growth. By design, the sampled black holes come from a period “corresponding to the peak of star formation and black-hole” growth in our roughly 13.7-billion-year-old universe, the scientists wrote. The most massive galaxies and their central black holes are widely believed to have grown through violent collisions with other galaxies, which trigger the formation of stars and provides food for the black holes to devour. These violent collisions would also have produced abundant dust, which briefly enshrouds the gorging black hole. The most spectacular, already known example of a dusty, growing black hole in the relatively nearby universe is the well-studied galaxy Markarian 231 located at a much smaller distance of 600 million light-years away, Banerji and colleagues said. A light-year is the distance light travels in a year. Studies with the Hubble Space Telescope indicate Markarian 231 crashed into another galaxy fairly recently in cosmic history. ULASJ1234+0907 is being described as a more extreme version of this nearby galaxy, indicating conditions in the early Universe were much more turbulent and inhospitable than today. The Cambridge researchers used infrared-light surveys being carried out on the U.K. Infrared Telescope to peer through the dust and locate the giant black holes for the first time. Infared light is a low-energy form of light not visible to the unaided eye. “These results are particularly exciting because they show that our new infrared surveys are finding super massive black holes that are invisible in optical surveys. These new quasars are important because we may be catching them as they are being fed through collisions with other galaxies,” said Richard McMahon at Cambridge, co-author of the study. He added that observations with the new Atacama Large Millimeter Array telescope in Chile “will allow us to directly test this picture by detecting the microwave frequency radiation emitted by the vast amounts of gas in the colliding galaxies.”