A team of astronomers from the UK has discovered a black hole of 350 million solar masses at the center of the galaxy SAGE1C J053634.78−722658.5 (SAGE0536AGN for short), which is about 2.3 billion light-years from Earth. According to the team, the black hole is much more massive than it should be, compared to the mass of the galaxy around it.
Vista Magellanic Clouds Survey view of the galaxy SAGE0536AGN (elliptical object in the center of the frame). Image credit: ESO / VISTA Magellanic Cloud Survey / Royal Astronomical Society.
SAGE0536AGN was discovered behind the Large Magellanic Cloud in 2011 by astronomers using NASA’s Spitzer Space Telescope.
Thought to be at least 9 billion years old, the galaxy contains an active galactic nucleus, an incredibly bright object resulting from the accretion of gas by a central supermassive black hole. The gas is accelerated to high velocities due to the black hole’s immense gravitational field, causing this gas to emit light.
Dr Jacco van Loon of Keele University and Dr Anne Sansom of the University of Central Lancashire have now confirmed the presence of the huge black hole by measuring the speed of the gas moving around it.
Using the Southern African Large Telescope, the astronomers observed that an emission line of hydrogen in the galaxy spectrum is broadened through the Doppler Effect. The degree of broadening implies that the gas is moving around at high speed, a result of the strong gravitational field of the black hole. These data have been used to calculate the black hole’s mass.
The mass of SAGE0536AGN itself, obtained through measurements of the movement of its stars, has been calculated to be 25 billion solar masses.
This is 70 times larger than that of the black hole, but the black hole is still 30 times larger than expected for this size of galaxy.
“Galaxies have a vast mass, and so do the black holes in their cores,” said Dr van Loon.
“This one though is really too big for its boots – it simply shouldn’t be possible for it to be so large.”
The discovery is reported September 8 in the online edition of the Monthly Notices of the Royal Astronomical Society (arXiv.org preprint).
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Jacco Th. van Loon & Anne E. Sansom. 2015. An evolutionary missing link? A modest-mass early-type galaxy hosting an oversized nuclear black hole. MNRAS 453 (3): 2341-2348; doi: 10.1093/mnras/stv1787
