Mighty Dons Of Science News

Which come first: the su­pe­r­mas­sive black holes that franti­c­ally de­vour mat­ter, or the huge ga­lax­ies where they re­side?

A new sce­nar­i­o has emerged to an­swer this con­ten­tious “‘chicken and egg’ ques­tion,” said Da­vid El­baz of the Cen­ter for Nu­clear Stud­ies of Saclay in Gif-sur-Yvette, France, one of the re­search­ers who de­vel­oped the mod­el.

the “black” mon­i­ker, but ac­tu­ally many black holes are thought to be easily vis­i­ble thanks to vi­o­lent ac­ti­vity go­ing on around them.





 Colour com­pos­ite im­age of qua­sar HE0450-2958, the bright­est ob­ject in the im­age. The im­age was ob­tained with the VISIR in­stru­ment on ES­O’s Very Large Tel­e­scope, the Hub­ble Space Tel­e­scope and the Ad­vanced Cam­era for Sur­veys. The qua­sar is be­lieved to be zap­ping the ob­ject to its low­er left, a gal­axy, with an en­er­get­ic beam of par­t­i­cles.

El­baz and col­leagues stud­ied a pe­cu­liar ob­ject some five bil­lion light years away, be­lieved to be a black hole with­out a home gal­axy and dubbed qua­sar HE0450-2958. A light year is the dis­tance light trav­els in a year.

It had been spec­u­lat­ed that the qua­sar’s host gal­axy was hid­den be­hind dust. The as­tro­no­mers thus used an in­stru­ment on the Eu­ro­pean South­ern Ob­ser­va­tory’s Very Large Tel­e­scope de­signed to de­tect so-called mid-infrared light, which would make dust clouds brightly vis­i­ble.

Yet no dust ap­peared, in­di­cat­ing there was no home gal­axy, said Knud Jahnke of the Max Planck In­sti­tute for As­tron­o­my in Hei­del­berg, Germany, who led the ob­serva­t­ions. “In­stead we dis­cov­ered that an ap­par­ently un­re­lat­ed gal­axy in the qua­sar’s im­me­di­ate neigh­bour­hood is pro­duc­ing stars at a frantic rate,” he said, the equiv­a­lent of about 350 Suns yearly.

Ear­li­er ob­serva­t­ions had shown that the com­pan­ion gal­axy is, in fact, un­der fire: the qua­sar is spew­ing a je­t of en­er­get­ic par­t­i­cles to­wards its com­pan­ion, ac­com­pa­nied by a stream of fast-mov­ing gas. The in­jec­tion in­di­cates that the qua­sar it­self might be in­duc­ing the forma­t­ion of stars and there­by cre­at­ing its own host gal­axy, ac­cord­ing to El­baz and col­leagues. In such a sce­nar­i­o, ga­lax­ies would have evolved from clouds of gas hit by the en­er­get­ic je­ts emerg­ing from qua­sars, or giant black holes.

“The two ob­jects are bound to merge in the fu­ture: the qua­sar is mov­ing at a speed of only a few tens of thou­sands of kilo­me­ters [or miles] per hour with re­spect to the com­pan­ion gal­axy and their separa­t­ion is only about 22,000 light-years,” said El­baz. “Although the qua­sar is still ‘naked’, it will even­tu­ally be ‘dressed’ when it merges with its star-rich com­pan­ion. It will then fi­nally re­side in­side a host gal­axy like all oth­er qua­sars.”

The find­ings may al­so rep­re­sent the long-sought mis­sing link to un­der­stand­ing why the mass of black holes is larg­er in ga­lax­ies that con­tain more stars, the re­search­ers added. “A nat­u­ral ex­ten­sion of our work is to search for si­m­i­lar ob­jects in oth­er sys­tems,” said Jahnke.

The findings are being pre­sented in new pa­pers pub­lished in the jour­nals Astro­nomy & Astro­physics and Astro­phys­ical Jour­nal.