Astronomers using NASA’s Wide-field Infrared Survey Explorer have discovered millions of supermassive black hole candidates across the Universe and about 1,000 hot dust-obscured galaxies.
“WISE has exposed a menagerie of hidden objects,” said Dr Hashima Hasan, WISE program scientist at NASA Headquarters in Washington. “We’ve found an asteroid dancing ahead of Earth in its orbit, the coldest star-like orbs known and now, supermassive black holes and galaxies hiding behind cloaks of dust.”
WISE scanned the whole sky twice in infrared light, completing its survey in early 2011. Like night-vision goggles probing the dark, the telescope captured millions of images of the sky. All the data from the mission have been released publicly, allowing astronomers to dig in and make new discoveries. The latest findings are helping astronomers better understand how galaxies and the behemoth black holes at their centers grow and evolve together.
In one study, astronomers used WISE to identify about 2.5 million actively feeding supermassive black holes across the full sky, stretching back to distances more than 10 billion light-years away. About two-thirds of these objects never had been detected before because dust blocks their visible light. WISE easily sees these monsters because their powerful, accreting black holes warm the dust, causing it to glow in infrared light.
In two other studies, astronomers report finding what are among the brightest galaxies known, one of the main goals of the mission. So far, they have identified about 1,000 candidates.
These extreme objects, called hot dust-obscured galaxies (DOG), can pour out more than 100 trillion times as much light as our sun. They are so dusty, however, that they appear only in the longest wavelengths of infrared light captured by WISE. NASA’s Spitzer Space Telescope followed up on the discoveries in more detail and helped show that, in addition to hosting supermassive black holes feverishly snacking on gas and dust, these DOGs are busy churning out new stars.
“These dusty, cataclysmically forming galaxies are so rare WISE had to scan the entire sky to find them,” said Dr Peter Eisenhardt, project scientist for WISE at JPL and lead author of the paper on the first of these bright, dusty galaxies. “We are also seeing evidence that these record setters may have formed their black holes before the bulk of their stars. The ‘eggs’ may have come before the “chickens.””
The WISE observations, combined with data at even longer infrared wavelengths from Caltech’s Submillimeter Observatory atop Mauna Kea, revealed that these extreme galaxies are more than twice as hot as other infrared-bright galaxies. One theory is their dust is being heated by an extremely powerful burst of activity from the supermassive black hole.
“We may be seeing a new, rare phase in the evolution of galaxies,” said Dr Jingwen Wu of JPL, lead author of the study on the submillimeter observations.
Stern et al. 2012. Mid-Infrared Selection of AGN with the Wide-Field Infrared Survey Explorer. I. Characterizing WISE-Selected AGN in COSMOS. Accepted to ApJ; arXiv: 1205.0811v1
Eisenhardt et al. 2012. The First Hyper-Luminous Infrared Galaxy Discovered by WISE. ApJ 755, 173; doi: 10.1088/0004-637X/755/2/173
Wu et al. 2012. Submillimeter Follow-up of WISE-Selected Hyperluminous Galaxies. ApJ 756, 96; doi: 10.1088/0004-637X/756/1/96