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Looking oddly like a smiley face, this image shows a pair of interacting galaxies in the process of merging into a single object. This system is called Markarian 739 (and NGC 3758) and lies at a distance of 425 million light years in the constellation of Leo.
It is thought that most large galaxies, our own included, actually contain a super-massive black hole. If enough material falls onto the central black hole, an enormous amount of energy is generated, and typically makes the nucleus more luminous that all the rest of the galaxy.
It has already been know for a few decades that this is happening in the eastern nucleus of Markarian 739 (left in photo) making it a so-called Active Galactic Nucleus (AGN). But now, a detailed study of the merging galaxies by a team at the University of Maryland in College Park (UMCP), under the direction of Michael Koss, shows that the other nucleus is also an AGN.
The crucial observations were made by the orbiting X-ray telescope Chandra, and the results will be published in The Astrophysical Journal Letters.
From data collected by the X-ray satellite Swift (that has also detected dozens of other AGN out to a distance of 650 million light years) it was already suspected that Markarian 739 contained a second active nucleus. However, the large field of view, and consequent low resolution of its sensors, prompted Koss and colleagues to use Chandra to observe the system at higher resolution. The confirmation of the second AGN is a demonstration of the importance of high resolution, high energy data.
According to a previous study by the same research team, about one quarter of the AGN identified by swift are in interacting galaxies or close galaxy pairs, and 60% of these could merge completely in the next billion years. Markarian 739 is only the second known example of a double AGN/super-massive black hole. The other is NGC 6240.
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