Scientists have shown that existing methods for analyzing data in the gamma range are unable to reliably exclude the contribution of a blurred signal, which could be caused by hypothetical annihilation of dark matter particles. As a result, conclusions about the pulsar nature of the observed excess radiation from the center of the Milky Way cannot be considered final, the authors write in the journal Physical Review Letters.
Dark matter is the name of a family of ideas designed to resolve a number of contradictions between observations and theoretical astrophysical estimates. The most popular option is to represent dark matter as undiscovered particles. At the moment, there is no direct confirmation of the presence of such objects.
According to the overwhelming majority of dark matter models, its particles should form extended halos, in which all galaxies, including the Milky Way, are immersed. In this case, a noticeable concentration of such particles should be observed at the center of the systems. At the same time, a number of theories suggest that interactions can occur between them, including annihilation. Its result should be the appearance of photons, whose energy will depend on the unknown mass of the original particles.
Similar signals were recorded, both in the X-ray range (a line of radiation in the direction of the Andromeda galaxy and the Perseus cluster), and in gamma (an excess of radiation from the center of the Milky Way). However, later the conclusion that these are traces of dark matter annihilation was considered unlikely, since it was shown that such features can appear as a result of the glow of a population of undetected millisecond pulsars.
MIT's Rebecca Leane and Tracy Slatyer showed that the previous analysis, co-authored by Slater, was also not without flaws. The article said that pulsars should look like fairly compact objects in the Fermi gamma-ray telescope, and deducting all known sources results in a pixel-by-pixel comparison of the remaining variations being much better explained by localized sources rather than the blurry glow expected for dark matter. …
It is theoretically assumed that dark matter is distributed according to a density function with a smooth profile, so its signal can be modeled with a Poisson distribution. However, populations of individual sources will generate a less uniform distribution, since due to the limited angular resolution with a nonzero probability, one pixel may contain several bright sources, and the other - none.
In the new work, the authors artificially added the expected dark matter signal to the real data, which was still identified by the program as belonging to pulsars. Moreover, the previously created algorithm continued to produce pulsars as a response, even if the artificial signal of dark matter was created with increased intensity, and only when the expected level was tenfold did it begin to be correctly determined. Scientists conclude that such an analysis does not give reliable results, so it is necessary to return to the initial position according to which the excess of gamma rays from the center of the Milky Way can still be associated with dark matter.
Previously, physicists used the image of the shadow of a black hole to set a limit on the mass of dark matter particles and found inconsistencies in the predictions of the theory of superfluid dark matter with observations of the Milky Way. We also did a special test on the main models of this component in the Universe - "What kind of dark matter are you?"