WISE J224607.55-052634.9 (W2246-0526 for short), the most luminous galaxy ever discovered, is accreting (eating) at least three of its smaller neighbors, according to a study led by Dr. Tanio Diaz-Santos of the Universidad Diego Portales, Chile.
An artist’s impression of W2246-0526, the most luminous galaxy ever discovered. Image credit: NRAO / AUI / NSF / S. Dagnello.
W2246-0526 was discovered in 2015 by NASA’s Wide-field Infrared Survey Explorer (WISE).
The light from this galaxy took approximately 12.4 billion years to reach Earth, so we are seeing it as it was when our Universe was only about a 1/10th of its present age.
W2246-0526 is by no means the largest or most massive galaxy astronomers know of, but it radiates at 350 trillion times the luminosity of the Sun.
New observations with the Atacama Large Millimeter/submillimeter Array (ALMA) reveal distinct streamers of material being pulled from three smaller galaxies and flowing into the more massive galaxy.
The connecting tendrils between the galaxies contain about as much material as the galaxies themselves.
“We knew from previous data that there were three companion galaxies, but there was no evidence of interactions between these neighbors and the central source,” said Dr. Díaz-Santos, lead author of a paper published in the journal Science.
“We weren’t looking for cannibalistic behavior and weren’t expecting it, but this deep dive with the ALMA observatory makes it very clear.”
This image, created using ALMA data, shows W2246-0526 as it syphons material away from three smaller galaxies; W2246-0526 and one of its companions are in the center, the second galaxy is above them and the third is to the lower left. Image credit: ALMA / ESO / NAOJ / NRAO / S. Dagnello / AUI / NSF.
The amount of gas being devoured by W2246-0526 is enough to keep it forming stars and feeding its central black hole for hundreds of millions of years.
This galaxy’s startling luminosity is not due to its individual stars. Rather, its brightness is powered by a tiny, yet fantastically energetic disk of gas that is being superheated as it spirals in on the supermassive black hole.
The light from this blazingly bright accretion disk is then absorbed by the surrounding dust, which re-emits the energy as infrared light.
This extreme infrared radiation makes W2246-0526 one of a rare class of quasars known as Hot, Dust-Obscured Galaxies (Hot DOGs).
Much of the dust and gas being siphoned away from the three smaller galaxies is likely being converted into new stars and feeding the larger galaxy’s central black hole.
This galaxy’s gluttony, however, may lead to its self-destruction. Previous research suggests that the energy of the active galactic nucleus (AGN) will ultimately jettison much, if not all of the galaxy’s star-forming fuel.
A separate study, led by University of California, Los Angeles researcher Chao-Wei Tsai, estimates that the supermassive black hole at the center of W2246-0526 is about 4 billion times the mass of the Sun.
“The mass of the black hole directly influences how bright the AGN can become, but W2246-0526 is about 3 times more luminous than what should be possible. Solving this apparent contradiction will require additional observations,” the astronomers said.
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T. Díaz-Santos et al. The multiple merger assembly of a hyperluminous obscured quasar at redshift 4.6. Science, published online November 15, 2018; doi: 10.1126/science.aap7605
Chao-Wei Tsai et al. 2018. Super-Eddington Accretion in the WISE-selected Extremely Luminous Infrared Galaxy W2246-0526. ApJ 868, 15; doi: 10.3847/1538-4357/aae698
