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Black hole army behind gamma ray excess summer ash.

Tribune News Service A FLOOD of gamma rays comes at us from the centre of the Milky Way, and dark matter smashing up at the edge of black holes may be partly to blame. Annihilation of weakly interacting massive particles (WIMPs), a leading contender for dark matter, can explain the overall shape of the gamma ray emissions we see. But spikes in the signal must be from other sources, possibly black holes or pulsars. Thomas Lacroix at the University of Montpellier and Joseph Silk at the Sorbonne University in Paris, both in France, now propose that these fluctuations come from a cluster of intermediate-mass black holes (IMBHs) within the central bulge of our galaxy. Lacroix and Silk calculate that about a thousand of these medium-sized holes in the innermost regions of the galaxy, with dark matter accumulating at their edges, should create enough gamma rays to account for the excess. Medium-sized black holes range from tens to hundreds of thousands of solar masses and are thought to form in the early universe as supernova remnants or as descendants of primordial black holes."The presence of IMBHs in the centres of galaxies isn't something many people talk about these days, even though they've been predicted," says Jillian Bellovary at the American Museum of Natural History."We haven't thought a lot about how dark matter might accumulate in clumps (aka density spikes) near IMBHs." Astronomers struggled to find evidence for these holes until the Laser Interferometer Gravitational-Wave Observatory (LIGO) first detected a merging pair in September 2015. LIGO has since detected three more pairs. If it spots these mergers in the centre of other galaxies, it could show that dark matter spikes near medium-sized black holes are indeed behind the gamma ray excess in our own galaxy.

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Publication:Qatar Tribune (Doha, Qatar)
Date:Mar 14, 2018
Words:309
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