Dark matter destruction has been ruled out as an origin of extra radiation in Milky Way’s galactic centre. In a paper recently published in the journal Physical Review D, the Kavil IPMU project researchers Oscar Macias and colleagues at other institutions report that; through the analysis of the Fermi data and an exhaustive series of modelling exercises; they were able to determine that the observed gamma rays could; not have been produced by what are called weakly interacting massive particles (WIMPS); most probably theorised as the stuff of dark matter.
Macias said “The crucial point of our recent paper is that; our approach covers the wide range of astrophysical background models; that have been used to infer the existence of the galactic centre excess, and goes beyond them. So, using any of our state-of-the-art background models; we find no need for a dark matter component to be included in our models; we find no need for a dark matter component to be included in our model for this sky region. This allows us to impose very stringent constraints; on particle dark matter models.”
The paper authors says that by eliminating these particles; the destruction of which could generate energies up to 300 gig-electron volts; they have put the strongest constraints yet on dark matter properties.
Co-author Kevork Abazajian, professor of physics and astronomy at the University of California says that “For 40 years or do, the leading candidate for dark matter among particles physicists was a thermal, weakly interacting and weak-scale particles, and this result for the first time rules out that candidate up to very high-mass particles.”
Co-author Manoj Kaplinghat, UCI professor of physics and astronomy added “In many models, this particle range from 10 to 1,000 times the mass of a proton, with more massive particles being less attractive theoretically as a dark matter particle. In this paper, we are eliminating dark matter candidates over the favoured range; which is a huge improvement in the constraints we put on the possibilities; that these are representative of dark matter.”
According to Abazajian the signals coming out from the dark matter could be crowded out by other astrophysical phenomena in the galactic centre such as star formation, cosmic ray deflection off molecular gas, and, most notably, neutron stars and millisecond pulsars as a source of excess gamma rays detected by the Femi space telescope.
Kavil IPMU’s Macias said that “We looked at all of the different modelling; that goes on in the galactic centre, including molecular gas; stellar emissions and high-energy electrons that scatter low-energy photons. We took over three years to pull all of these new; better models together and examine the emissions, finding that there is little room left for dark matter.”
All the classes of models used in the galactic centre region were tested by the group for excess emission analyses. And its conclusion remained untouched. Macias said “One would have to craft a diffuse emission model; that leaves a big ‘hole’ in them to relax constraints, and science doesn’t work that way.”
After all this, the research doesn’t rule out the existence of dark matter in the galaxy. Kaplinghat said, “No, our study constraints the kind of particle that dark matter could be. The multiple lines of evidence for dark matter in the galaxy are robust and unaffected by our work.”